PERSPECTIVES

Reginald Crundall Punnett: First Arthur BalfourProfessor of Genetics, Cambridge, 1912

A. W. F. Edwards1

Gonville and Caius College, Cambridge CB2 1TA, United Kingdom

ABSTRACT R. C. Punnett, the codiscoverer of linkage with W. Bateson in 1904, had the good fortune to be invited to be the firstArthur Balfour Professor of Genetics at Cambridge University, United Kingdom, in 1912 when Bateson, for whom it had beenintended, declined to leave his new appointment as first Director of the John Innes Horticultural Institute. We here celebrate thecentenary of the first professorship dedicated to genetics, outlining Punnett’s career and his scientific contributions, with specialreference to the discovery of “partial coupling” in the sweet pea (later “linkage”) and to the diagram known as Punnett’s square. Hisseeming reluctance as coauthor with Bateson to promote the reduplication hypothesis to explain the statistical evidence for linkage isstressed, as is his relationship with his successor as Arthur Balfour Professor, R. A. Fisher. The background to the establishment of theProfessorship is also described.

THE centenary of the foundation of Cambridge Univer-sity’s Professorship of Genetics in 1912 provides a timely

occasion to recall the contributions of its first holder,Reginald Crundall Punnett (1875–1967; Figure 1). Over-shadowed by his senior colleague William Bateson (1861–1926), for whom the Professorship had been intended, andhis successor R. A. Fisher (1890–1962), Punnett played animportant role in the early days of Mendelian genetics. Hewrote the first genetics textbook Mendelism (Punnett 1905),collaborated in the discovery of partial coupling (linkage),asked G. H. Hardy the question that led to the formulationof what became known as Hardy–Weinberg equilibrium,published Mimicry in Butterflies (Punnett 1915) and Hered-ity in Poultry (Punnett 1923a), and pioneered the use of sex-linked markers for sexing poultry chicks. He founded theJournal of Genetics with Bateson in 1911 and edited it aloneafter Bateson’s death. He was the first Secretary and waslater President of the Genetical Society of Great Britain. Hisname is immortalized in “Punnett’s square” (Figure 2).

F. A. E. Crew (Crew 1967) wrote Punnett’s biographicalmemoir for the Royal Society, to which Punnett was electedin 1912, and followed this with a shorter account forGENETICS (Crew 1968). In the opening paragraph of thelatter he said that Punnett “had the good fortune to be anactive participant in the work that confirmed and extended

the findings of Gregor Mendel when these were brought tolight in 1900. He lived, therefore, in a period that was filledwith excitement and could rightly feel that he was involvedin a great adventure that would surely lead to a revolutionin biological thought.” Crew’s memoirs should be consultedfor details of Punnett’s life; here I concentrate on hisscientific contributions and give only a brief biographicalsummary.

Brief Biography

Punnett was born to George and Emily Punnett (néeCrundall) at Tonbridge, Kent, on June 20, 1875. Bothparents were of Kentish stock. He was educated at CliftonSchool, Bristol, and Gonville and Caius College, Cambridge,which he entered as a scholar in 1895. Originally registeringas a medical student, he took the Natural Sciences Tripos,specializing in zoology in his third year and being placed inthe first class in the Tripos in 1898. He spent the next year atthe Naples Zoological Station (Naples, Italy) and at Heidel-berg University (Heidelberg, Germany) and in September1899 accepted the post of Demonstrator in the Natural His-tory Department of the University of St. Andrews (St.Andrews, Fife, Scotland). In October 1901 a Fellowship ofGonville and Caius College followed, capped by the Univer-sity post of Demonstrator in Morphology, which he held un-til 1904, when he became Balfour Student in Zoology. Thisstudentship, in memory of Francis Balfour, Professor of

Copyright © 2012 by the Genetics Society of Americadoi: 10.1534/genetics.112.1435521Address for correspondence: awfe@cam.ac.uk

Genetics, Vol. 192, 3–13 September 2012 3

Animal Morphology, Arthur Balfour’s brother, had been heldby William Bateson from 1897 to 1900.

Then in 1908 Punnett started a rapid rise up theacademic ladder. Still with his Caius Fellowship (which hewas to retain until his death) he became Demonstrator inAnimal Morphology in the Department of Zoology, Superin-tendent of the Museum of Zoology in 1909, and, whenBateson resigned his Professorship of Biology in 1910 to takeup the Directorship of the John Innes Institute, Punnettsucceeded to it. In 1912 the Arthur Balfour Professorship ofGenetics was founded and, following the failure of theUniversity to attract Bateson back from his Directorship,Punnett was appointed. We consider the history of theProfessorship in a later section.

At Naples in 1899 Punnett started to study the morphol-ogy of nemertine (or “Nemertean”) marine worms, andthese continued to be his main interest at St. Andrews andon his return to Cambridge. In 1903 he embarked on a sta-tistical study “On nutrition and sex-determination in man,”using data for London from the 1901 Census, whichrevealed a modest facility in handling numbers (Punnett1903). The human sex ratio was my own Ph.D. topic andin 1959 I must have heard about his interest and sent him anoffprint of one of my articles (Edwards 1958) for I still havehis letter in reply.

Punnett’s association with Bateson started at the begin-ning of 1904. Some time earlier, “Knowing that Bateson was

carrying out Mendelian experiments at Merton House,Grantchester, [Punnett] wrote to him suggesting that per-haps his nutritional experiments might be so designed thatthey would yield information concerning the inheritance ofcoat colour [in the mouse]” (Crew 1967). When Batesonreceived an offer of financial support from his friend Mrs.Christiana Herringham in December 1903, he first thoughtof Leonard Doncaster as an associate, but Doncaster de-clined (Cock and Forsdyke 2008, p. 217) and so he wroteto Punnett (on Christmas Day), inviting him to come “intopartnership in my breeding experiments.” “Mr. Punnettjoined with enthusiasm, and very generously refusedthe ... salary” (Bateson 1928, p. 87), “... and so a partnershipthat was to last six years and that was to make notable andenduring contributions to genetics came into being. The twomen were very different temperamentally, Bateson wasa forceful personality, combative and stern; Punnett was re-tiring, tolerant and friendly; it was a happy and harmoniouspartnership” (Crew 1967).

In 1913 Punnett married Eveline Maude Froude, widowof Sidney Nutcombe-Quicke. They lived in WhittingehameLodge, Storey’s Way, Cambridge, in the house provided forthe Arthur Balfour Professor, until Punnett retired in 1940 atthe age of 65. He and his wife then moved to Bilbrook, nearMinehead, Somerset, where he died on January 3, 1967.There were no children.

Crew’s (1967) biographical memoir contains a list ofPunnett’s publications and summaries of his work beyondthe topics I discuss in detail here. In the summer of 1909Punnett had visited Ceylon to study mimetic butterflies,where he met his Caius colleague R. H. Lock, then AssistantDirector of the Royal Botanical Gardens at Peradeniya(Sri Lanka). The visit led to a handsomely illustrated book-Mimicry in Butterflies (Punnett 1915). “... it included a

Figure 1 R. C. Punnett. Courtesy of the Master and Fellows of Gonvilleand Caius College, Cambridge.

Figure 2 Punnett’s square, from the Second Edition of Mendelism(Punnett 1907).

4 A. W. F. Edwards

mutationist’s explanation for the evolution of complex mi-metic resemblances between members of unrelated species”(Bennett 1983, p. 8). R. A. Fisher’s view of their evolutionwas completely different. He set it out in Fisher (1927) andin Chapter VIII, “Mimicry,” of The Genetical Theory of NaturalSelection (Fisher 1930a) with special reference to Punnett’sview in the section “The theory of saltations.” Provine(1971, p. 150) gives an account. On evolution Fisher andPunnett were to cross swords again when Punnett reviewedThe Genetical Theory, which we refer to below under Popu-lation Genetics.

Punnett’s experience with studying Mendelian charactersin poultry led him to invent the method of using sex-linkedplumage color factors to sex day-old chicks, thus enablingthe unwanted majority of cockerels to be disposed of imme-diately. By 1940 he had published, alone or jointly, 11 “Ge-netic studies in poultry,” with another two to come inretirement in 1948 and 1957. Crew (1968) may be referredto for further details, for unlike the biographical memoir forthe Royal Society his memoir in GENETICS contains a sub-stantial extract by Professor F. B. Hutt “whose Genetics of theFowl is in the direct line of Punnett’s Heredity in Poultry,1923a” (Crew 1968).

Punnett (1928) edited Bateson’s scientific articles forCambridge University Press. T. H. Morgan (1929) reviewedthe two volumes in Nature, regretting the omission of theReports to the Evolution Committee (see below), whichwere represented only by summaries. After Bateson’s deathin 1926, Punnett (1926) wrote a memoir of him in theEdinburgh Review, part of which was reprinted in Notesand Records of the Royal Society in 1952 (Punnett 1952).

Punnett’s Square

he work for which Punnett is best remembered, thediscovery of linkage jointly with William Bateson, aroseout of their studies of Mendelian ratios in the sweet peaLathyrus odoratus. The discovery is more properly referredto as “partial coupling” because the word “linkage” had notyet been coined in this connection, nor had its chromo-somal basis been postulated. The analysis of the variousratios that characterized Mendelian inheritance was muchfacilitated by Punnett’s simple square diagram showinghow gametes combine to make zygotes or sometimeshow genotypes at two loci combine to make zygotes. Pun-nett’s square seems to have been a development of 1905,too late for the first edition of his Mendelism (May 1905)but much in evidence in Report III to the Evolution Commit-tee of the Royal Society [(Bateson et al. 1906b) “receivedMarch 16, 1906”]. The earliest mention is contained ina letter to Bateson from Francis Galton dated October 1,1905 (Edwards 2012). We have the testimony of Bateson(1909, p. 57) that “For the introduction of this system [the‘graphic method’], which greatly simplifies difficult cases, Iam indebted to Mr. Punnett.” As we shall see, 1905 wasalso an important year in the discovery of partial coupling,

so the two developments went hand in hand. Here wegive the salient features of Punnett’s square, relying onthe extended account by Edwards (2012), which is fullyillustrated.

The first published diagrams appeared in 1906. OnFebruary 1 Bateson, in an address to the NeurologicalSociety (Bateson 1906), displayed the 9:3:3:1 Mendelianratio among the F2 for two loci when dominance is completeat both. Then Report III contained several, notably the oneson p. 3 (our Figure 3) and p. 10. Figure 3 displays the 9:7ratio obtained when, to quote the figure legend, “The char-acter, colour for example, appears only when C and R meet.”We consider the more complex figure on p. 10 in a moment.Figure 3 was repeated by Lock (1906, p. 199) in his bookRecent Progress in the Study of Variation, Heredity, and Evo-lution, the Preface being dated October 23. It will be notedthat these squares are formed by the simple process of layingout the four gametotypes CR, cR, Cr, cr as headings for bothrows (paternal gametes, say) and columns (maternal game-tes) and “adding” them to create the entries in the squarescorresponding to the zygotes formed by their unions.

However, when Punnett published the second edition ofhis Mendelism, he used a slightly different format (our Fig-ure 2; Punnett 1907, p. 45) also displaying 9:3:3:1. It isdivided into four large squares each of which contains foursmall squares. Each large square is identical in respect to thesecond locus, B,b, and shows the two types of gamete unit-ing to form zygotes, two of which, Bb and bB, are identical ifgametic origin is ignored. The four large squares do thesame for the first locus A,a, and then the four small squaresfor B,b are added to each of the large squares for A,a. Ofcourse it comes to the same thing as Figure 3, the differencebeing only a matter of the labeling. In the third edition(Punnett 1911, p. 34) he reverted to the arrangement ofFigure 3 complete with a description of the construction of

Figure 3 Punnett’s square, from Report III (Bateson et al. 1906b).

Perspectives 5

what he called the “chessboard” method (although in truthit is more like a multiplication table).

When three loci are involved, an 8 · 8 square results, asgiven in Report III on p. 10 (Figure 4). This is an extremelyinteresting construction. Thinking of it as four large squares,we see that in respect to B,b and R,r, each of these squares isthe same, but different from either of the methods of con-structing a two-locus table so far described (in fact there isan error in columns 7 and 8, where the lower entries in row5 have been interchanged). Instead of the union of gameteswe have the union of loci, the rows for R,r, and the columnsfor B,b. Then each of these squares has been dropped intoa square for C,c as in Punnett’s (1907) construction (Figure2). This hybrid format was suggested by Sir Francis Galtonin a letter to Bateson dated October 1, 1905 containing theoriginal of Figure 4 (reproduced in Edwards 2012). It is oddthat when it was published, in Report III and later, Galton’shelp was not acknowledged.

To appreciate the significance of Galton’s arrangementit is necessary to describe the situation that confrontedBateson and Punnett, and since the experiments involvedare the very ones that led to the discovery of partial cou-pling, this serves as an introduction to the next section. “Thework was begun,” wrote Bateson in his book Mendel’s Prin-ciples of Heredity (Bateson 1909, p. 89), “by crossing twowhite sweet peas belonging to the variety Emily Henderson.These plants were alike in every respect so far as could beperceived, excepting that the shapes of the pollen grainsdiffered, the one having the normal long pollen grains ofthe species, while the other had roundish grains. The objectof the experiment was to trace the descent of the pollen-character and at the beginning no question of colour wasentertained. When F1 was grown however it was clear thathere was a remarkable opportunity of studying a reversionin color due to crossing, for these plants instead of beingwhite were purple like the wild Sicilian plant from whichour cultivated sweet peas are descended.”

Proceeding to the F2, Bateson and Punnett found “phe-nomena [which] . . . presented superficially an appearanceof great complexity. . . . It is unnecessary to go through thelong series of steps by which the analysis of the phenomenawas carried out. The meaning of the facts is now perfectlyclear and they can all be arranged in one consistent scheme”(Bateson 1909, p. 90). They worked out that three lociwould do. The two original whites were CCrrBB andccRRbb, leading to F1 all CcRrBb. On selfing, these wouldlead to the 64 combinations shown in Figure 4. In the pres-ence of C (for color?) the situation is always that R (red)dominant to r gives a red flower to which B (blue) dominantto b adds blue to make a purple flower, although in theabsence of R there is no blue alone. This is then the patternin the three large squares corresponding to CC, Cc, and cC.In the fourth, cc, no colors of any kind appear. We end upwith 3 · 9 = 27 purples, 3 · 3 = 9 reds, and 3 · 4 + 16 = 28whites. The numbers given in Report III are 1634, 498, and1593, respectively, 3725 in all, against expectations of 1571,

524, and 1630 (x2 on 2 d.f. = 4.59, P = 0.10; all values ofx2 quoted here are newly calculated).

Partial Coupling (Linkage)

It is frequently said that linkage was discovered by Batesonand Punnett in 1905. Thus A. H. Sturtevant himself, writing AHistory of Genetics in retirement (Sturtevant 1965), records(p. 40) that “Incomplete linkage was first reported in thesweet pea by Bateson and Punnett (1905),” but already somequalifications are needed. First, “in the sweet pea” needs to bein parentheses, or at least between commas, because this wasthe first report of partial linkage in any organism. Second, thereference is actually to Bateson et al. (1905), as given bySturtevant in his bibliography, which raises the question ofthe contribution of Saunders. (Morgan 1928, in The Theory ofthe Gene, p. 323, went further and omitted Saunders from thereference too.) Third, the word linkage in its genetical contexthad not, in 1905, been coined and is associated with thechromosomal theory advanced by Morgan (1911), who eventhen still used the term “coupling.” The first use of linkage inthis connection is in 1912 (Morgan and Lynch 1912), but weshould note that Bateson (1906) had written “We have proofthat in certain cases a character, say of shape, may be solinked or coupled with another character, say of color, thatall or a majority of the germs [gametes] which carry the onecarry the other also.” Punnett (1911, p. 87), in the thirdedition of his Mendelism, wrote “In some way or other thefactors for blue and for long pollen become linked together inthe cell divisions that give rise to the gametes, but the linkingis not complete.”

In the present account I use coupling for the statisticalevidence as opposed to its chromosomal explanation, and,

Figure 4 Galton’s three-locus square from Report III (Bateson et al.1906b).

6 A. W. F. Edwards

like Bateson and Punnett, I distinguish between completecoupling and partial coupling. This distinction is important,because complete coupling had already been found byCorrens (1900) in stocks (Matthiola) as noted by Batesonand Saunders (1902), who reported similar “correlation” intheir own experiments with stocks. Correns had used theword “gekoppelte.” Although this 1902 Report to the Evolu-tion Committee of the Royal Society (Bateson and Saunders1902) was the joint work of Bateson and E. RebeccaSaunders (“Becky”), Part I, in which the correlation wasnoted, is headed “Experiments with Plants, carried out byE. R. Saunders,” to whom therefore we may attribute theobservation.

Partial coupling appears for the first time in Report II tothe Evolution Committee (Bateson et al. 1905; received May18, 1904), the one to which Sturtevant referred. It containsno further reference to correlation in its Matthiola section,but in the section on sweet peas we read “There is, therefore,some coupling of pollen-shape and colors” (italics original)(Bateson et al. 1905, p. 89). This section is headed “Experi-ments carried out by W. Bateson, E. R. Saunders, and R. C.Punnett (in 1904).” It is evident that many additions to Re-port II were made after May 1904, including a “Note addedDecember 1904” at the end. The earliest mention of dis-turbed segregations corresponding to this coupling is inBateson’s Report to the Committee on Experimental Studiesin the Physiology of Heredity at the British Association meet-ing in Cambridge in August 1904 (Bateson 1905) and hisPresidential Address to the Zoological Section at the meet-ing (also reproduced in Bateson 1928; the mention is on p.255).

Then in Report III (Bateson et al. 1906b; received March16, 1906) there is a full section on “Gametic Coupling,”which starts “Early in the revival of breeding experiments,attention was called, especially by Correns, to the phenom-enon of coupling between characters. .... Examples of partialcoupling have not hitherto been adequately studied. A re-markable case occurs in regard to the distribution of thepollen-characters in F2 from the white long x white roundSweet Pea” (Bateson et al. 1906b, p. 9), and the results areprinted. More information is given in the later section ofReport III devoted to the sweet pea itself (“Experiments byW. Bateson, E. R. Saunders and R. C. Punnett”). The crucialresults had in fact appeared earlier in a brief note in Proceed-ings of the Royal Society, Series B (Bateson et al. 1906a; re-ceived December 1 and read December 7, 1905).

Finally, Report IV (Bateson et al. 1908) contains, in itsintroduction, a brief review of work on partial coupling,which starts “The majority of our Sweet Pea work of thepast two seasons was undertaken with a view to furtherelucidating the phenomenon we have termed gametic cou-pling” (Bateson et al. 1908, p. 2). The section on sweet peasis headed “Experiments by W. Bateson and R. C. Punnett”and contains a subsection “Partial Gametic Coupling.”

There is some slight evidence that Sturtevant, in his His-tory, might knowingly have credited this discovery of partial

coupling to Bateson and Punnett, omitting Saunders. Al-though Saunders was the undoubted Queen of Matthiola,Punnett does seem to have been King of L. odoratus. Sturte-vant (1965, Author’s Preface, p. xi) had “some direct per-sonal contact” with Bateson and Punnett and had metSaunders, although she counted among those he “never re-ally knew.” Bateson (1906), when discussing color in thesweet pea, refers to “an elaborate series of experimentsmade by Miss Saunders, Mr. Punnett, and myself,” but inthe corresponding part of his book Mendel’s Principles ofHeredity (Bateson 1909, p. 89) he refers to experiments ashaving been “carried on jointly by Mr. Punnett and myselffor some years.” Nor is there any sense that he is inclined toneglect Saunders’ work, for the next section (Bateson 1909,p. 95) on “Colors of Stocks” (Matthiola) starts “The experi-ments of Miss E. R. Saunders have revealed ... .” For furtherinformation about Saunders see Richmond (2001, 2006)and references therein. Lock (1906, p. 200), a member ofBateson’s group at the time, says firmly “This phenomenonof partial gametic coupling was discovered by Bateson andPunnett in the Sweet Pea.” Punnett (1914) himself wascharacteristically self-effacing: “Bateson in 1905 was thefirst to describe in sweet-peas a remarkable case in whichtwo characters each exhibiting ordinary Mendelian segrega-tion nevertheless showed a peculiar distribution with regardto one another.” Report II refers to “the original crosses of1901.” Punnett joined the sweet-pea work in 1904, growingthe F2 in which he and Bateson noted the disturbed segre-gations, so the F1 must have been 1903, which would makethe original cross 1902. Perhaps there were some in both1901 and 1902.

In his reminiscences “Early days of genetics” given at thehundredth meeting of the Genetical Society at Cambridge in1949, Punnett (1950) said “Sweet peas were the other mainline of inquiry. We grew some thousands each year and ofcourse the garden at Merton House [the Bateson home inGrantchester] could not nearly accommodate such num-bers.” He goes on to describe the additional plots on theUniversity Farm at Impington, four miles away, and the ridethere “for a long afternoon, Bateson with his wife in thetrailer carrying the ‘Farm Book’ and a microscope.” “Oneof us pulled the plant and sung out its characters andhanded the plant to the other, who, with the microscopeperched on some odd box picked up at the farm, determinedthe shape of the pollen. All duly logged by Mrs. Bateson”(Punnett 1950).

The “Farm Books” and allied notebooks recording exper-imental data are preserved in Cambridge University Libraryand might provide further information about the partici-pants, if only by the handwriting. But no doubt they allhelped each other, and it looks as though Mrs. Bateson de-served a formal mention too.

Bateson and Punnett found an F2 segregation 2844 longpollen and 881 round, against 3:1 expectations of 2794 and931, respectively (x2 on 1 d.f. = 3.62, P = 0.057). As wehave seen, in the field they scored the color before the

Perspectives 7

pollen type so it would be natural to have three columns forthe colors, each divided into two for the pollen type, and thisis how the data were presented in Report III (Table 1). Theynoted that the 3:1 ratio did not hold for the three color typesindividually. There seemed to be some kind of coupling ofround with red and long with purple that was disturbing theMendelian segregations; white seemed to be unaffected.Bateson and Punnett’s explanation was that B (blue) and L(for long) tended to associate in the gametes, as did theirrecessive counterparts b and l (round). The converse to thiscoupling was the “repulsion” of B and l, b and L.

They were familiar with Mendel’s law of independentsegregation and with the complete coupling reported byCorrens and by Saunders, but here was something in be-tween, partial coupling. “The significance of such partialcoupling is obscure, and it may result from several pro-cesses, between which no discrimination can yet be made”(Bateson et al. 1906b, p. 9) (Report III). But it could bemeasured, and Bateson and Punnett found that if gameteswere produced in the ratio 7BL:1Bl:1bL:7bl, the resultingphenotypic ratio 177BL:15Bl:15bL:49bl fitted the observednumbers (Table 1) quite nicely. The calculation of the phe-notypic ratio from the gametic for an F2 segregation is nowan elementary student exercise, but Report III did not ex-plain it, and neither did Bateson (1909) in his book. Thegeneral result for the gametic ratio

ðn2 1ÞBL :1Bl :1bL : ðn2 1Þbl

was given in Report IV (Bateson et al. 1908) and by Punnettin the third edition of Mendelism, with a full explanation forthe above case (Punnett 1911, Appendix to Chap. IX, p. 88):

3n22 ð2n2 1ÞBL : ð2n2 1ÞBl : ð2n2 1Þ bL : 3n2 2 ð2n2 1Þ bl:

(In fact, Punnett has a sign wrong in the gametic ratio.)Following Bridges (1914), nowadays we would use the re-combination fraction u = 1/n with the gametic ratio

12ð12 uÞ : 1

2u :

12u :

12ð12 uÞ

to give the familiar

12þ14ð12uÞ2: 1

2u2

14u2 :

12u2

14u2 :

14ð12uÞ2:

Alas, it did not occur to Bateson and Punnett that the “sev-eral processes” they could contemplate for the explanation ofpartial coupling need not be limited to integral values of n, andthey became fixated on the further idea that n had to bea power of 2 [“pure numerology brought about by a fixationon Mendelian ratios” (Edwards 1996)], for they began tovisualize processes of gametogenesis that required this asan explanation, their so-called “reduplication” hypothesis(Bateson and Punnett 1911; see below). If they had kept anopen mind and allowed any value of n, or better still worked

with the simpler u, they would have been free to choose thebest value without restriction. As late as March 1911, the dateof the Preface to his third edition of Mendelism, Punnett writes(Punnett 1911, p. 87) “Nor for the present can we suggest whycertain factors should be linked together in the peculiar waythat we have reason to suppose that they are during the pro-cess of the formation of the gametes.”

Weldon (1902) had already applied Karl Pearson’sgoodness-of-fit test to Mendel’s data, so that Bateson andPunnett could have chosen the value that gave the best fit bythe criterion of x2, thereby inventing the method of mini-mum x2 nearly a decade before Engledow and Yule (1914)did so (reprinted with a commentary by Edwards 1997). Butthat would have been stealing the biometricians’ clothes.

We conclude by noting that Punnett made a very pre-scient remark about partial coupling when addressing theEpidemiological Section of the Royal Society of Medicine onFebruary 28, 1908, 3 years before Morgan’s chromosomallinkage theory. “Enough, however, is known to make it cer-tain that it [partial coupling] often plays an important partin heredity, and I have laid some stress upon it because itmay eventually be found to throw light upon the allegedassociation of certain physical peculiarities in man with par-ticular forms of disease” (Punnett 1908). The comment fore-shadows the suggestion by Fisher (1935) in “Linkage studiesand the prognosis of hereditary ailments” read to the Inter-national Congress on Life Assurance Medicine (see Edwards2004, for Haldane’s possible contribution), which in turnforeshadowed the similar suggestion by J. H. Edwards(Edwards 1956) in connection with detecting marker lociin amniotic cells. For if a disease gene is linked closelyenough to a marker locus, knowledge of the marker geno-type may help in the prognosis of a disease not yet manifest.Punnett also remarked, in 1907 (Mendelism; Punnett 1907,p. 64), that “there is every probability that, as it [partialcoupling] becomes better known, it will be found of peculiarimportance in the elucidation of the architecture of the gam-ete.” In his last edition (Punnett 1927, p. 135) he remindedus of this by quoting it, adding “How brilliantly this pre-diction has been fulfilled by Professor Morgan and hiscolleagues will appear in the following chapter [the chro-mosome theory].”

The Reduplication Hypothesis

For many years neither Bateson nor Punnett accepted thechromosomal explanation of linkage, and by “coupling” and“repulsion” they meant statistical associations as observed inthe sweet pea. In a talk in 1959 Punnett said “I have

Table 1 F2 segregation in the sweet pea for flower colorand pollen type

Purple Red White

Long Round Long Round Long ound1528 106 117 381 1199 394

8 A. W. F. Edwards

sometimes been asked how it was that having got so far wemanaged to miss the tie-up of linkage phenomena with thechromosomes. The answer is Boveri. We were deeplyimpressed by his paper ‘On the Individuality of the Chromo-somes’ and felt that any tampering with them by way ofbreakage and recombination was forbidden” (Punnett1950). In 1911 they advanced their “reduplication” hypoth-esis to explain coupling and its mirror phenomenon, repul-sion. Its origin can be seen in some comments by Bateson inMendel’s Principles of Heredity (1909, pp.157–161), but thedefinitive account is in Bateson and Punnett (1911). By thetime Whitehouse (1965) wrote his magisterial Toward anUnderstanding of the Mechanism of Heredity it had been for-gotten. We use Sturtevant’s (1965) historical account:

According to the reduplication hypothesis, segregationdoes not occur at the time of meiosis but somewhat earlier,and not necessarily at the same time for each pair of genes.The cells that are finally produced, each with a single set ofgenes, then multiply at different rates to give the observedratios. It is not easy to see why this scheme was developed,since there is nothing in it that seems related to the (2n–1):1 series, nor is there any independent evidence for thecomplex and symmetrical pattern of divisions that itrequires. The hypothesis is related to Bateson’s reluctanceto believe that segregation occurs at the meiotic divisions(Sturtevant 1965, p. 40).

Sturtevant continues with further comments on Bateson’sthinking. For more information about the hypothesis andBateson’s reluctance to accept the chromosome theory seeCock (1983), who, interestingly, headed his section on it“Bateson’s own rival theory,” and Cock and Forsdyke(2008). The best that can be said for the theory is that itseems to have spurred Morgan on to have his eureka mo-ment in 1911 with the chromosomal explanation of linkage.

Punnett himself never incorporated reduplication into thelater editions of his Mendelism, limiting his discussion toobservations on the numerical ratios thought to be occur-ring. He pursued the question with further experiments insweet peas (Punnett 1913, 1917a), but by the second ofthese articles he was already considering Morgan’s explana-tion of linkage, and in the fifth edition of Mendelism(Punnett 1919, p. 133) he introduced a new chapter, “TheChromosome Theory” “to present the position of the sup-porters of the chromosome theory ... [which] is, at the pre-sent moment, the most keenly discussed question inheredity.” But the controversy was not really being discussedany more, and one senses that his heart was not in redupli-cation and he simply did not want to upset Bateson.

Bateson (1922) famously abandoned his doubts “aftera week in close communion with the wonders of ColumbiaUniversity” visiting Morgan’s laboratory. The observations ofthe Belgian cytologist F. A. Janssens published in 1909 hadpersuaded Morgan and most other people of the existence ofcrossing-over sufficient to account for the observed linkagephenomena, even though doubt remained about Janssens’precise model (see the Perspectives by Koszul et al., 2012, in

GENETICS, Vol. 191, Num. 2). Morgan was to write, in TheTheory of the Gene (Morgan 1928, p. 41) “From the nature ofthe case it is practically impossible to demonstrate, evenwhen twisting of the chromosomes is admitted, that it actu-ally leads to an interchange of the kind demanded by thegenetic evidence.”

What did Punnett really think? According to Cock (1983)“At no time did Punnett show any great interest in chromo-somes,” and I suspect that Punnett, who possessed “a blithe,kindly, open-air personality” (Needham 1967) quite unlikethe combative Bateson, might simply have opted for a quietlife. Cock (1983) continued “He is unlikely, therefore, tohave given Bateson any stimulus toward a more favorableview of chromosome theory.” There is also the possibilitythat he was sensitive to the view of his friend Lock, whohad suggested as early as 1906 (Lock 1906, p. 252) thatcoupling might be due to “some mechanism which causesthe representative particles of the respective characters con-cerned to remain in company during the process by whichthe other allelomorphs are being reassorted between thechromosomes,” as had been noted by Morgan and his col-leagues (Sturtevant 1965). Even when describing thezygotic ratios arising from gametic coupling in his 1919edition of Mendelism, Punnett (1919, p. 124) does not de-scribe the reduplication hypothesis, merely saying “Morerecently the term ‘reduplication’ has been brought intouse. . . .. The term is not altogether satisfactory, for biologistsare not at present in agreement as to the manner in whichthese gametic series come to be formed.” Torn betweenBateson and Lock, it would have been charactistic of Punnettto have kept his head down, and in any case from 1911Bateson was at the John Innes Institute and not in Cambridge.

The Arthur Balfour Professorship of Genetics

The prehistory of the Arthur Balfour Professorship starts notwith Punnett, but with Bateson, whom the University madea Reader in 1908. In their Report the recommending body,the General Board, had said that “they regret that in view ofthe state of University finances they cannot propose at thepresent time to establish a Professorship in Heredity andVariation” (Cambridge University Reporter 1907–1908, p.213). The academic and political background to this ap-pointment is fully described by Cock and Forsdyke (2008,p. 303). Evidently wheels were turning behind the scenes,for on February 24, 1908 the University’s Council was ableto publish a report “on a proposed Professorship of Biology”(Cambridge University Reporter 1907–1908, p. 632; reprin-ted in part in Cock and Forsdyke, p. 306). An anonymousbenefactor, likely to have been Arthur Balfour, had offered tosupport in part a Professorship to be devoted to “that branchof Biology now entitled Genetics (Heredity and Variation)”for 5 years in connection with the celebration of the Darwincentenary in 1909. Indeed, he wanted it to be the “DarwinProfessorship,” but the Council thought a title should waituntil “the professorship can . . . be placed on a permanent

Perspectives 9

footing.” The duty of the Professor was quite specific: “topromote by teaching and research the knowledge of Genet-ics.” It was less than 3 years since Bateson had coined theword. The Professorship was clearly intended for him, andhis election was announced on June 8. He gave his Inaugu-ral Lecture “The Methods and Scope of Genetics” on October23 (Bateson 1908) and it is from 1908 that Cambridge’sProfessorship of Genetics really dates. For Punnett the “mu-sical chairs” of posts led to the changes already mentioned inthe biographical section above, culminating in his election tothis Professorship of Biology when Bateson resigned it totake up the Directorship of the new John Innes HorticulturalInstitute in 1910.

Arthur James Balfour (1848–1930) was Prime Ministerfrom 1902 to 1905, a brilliant aristocratic intellectual whoheld a key position in the Conservative party for nearly fiftyyears. He was the elder brother of Francis Balfour, who hadlost his life in a climbing accident in 1882 soon after becom-ing Cambridge’s Professor of Animal Morphology. He hadtaught the undergraduate Bateson. Arthur Balfour’s manyconnections included his brother-in-law Lord Rayleigh,Chancellor of the University at the time of the Darwin Cen-tenary, an office to which he himself succeeded in 1919. Hewas President of the British Association at the time of the1904 Cambridge meeting and the foundation President ofthe Genetical Society in 1919, being succeeded on his deathby Punnett. Among his undergraduate friends he countedGeorge Darwin, with whom he played real (“court”) tennis,and George had taken him to visit his father Charles Darwinat his house in Downe, Kent. “The kindness of the greatman, his sympathy and charm, exceeded all that could bedemanded by the most self-centered guest, and left a deepimpression on my youthful mind” (Balfour 1930, p. 38).Bateson could not have had a more powerful friend at courtthan Arthur Balfour.

During the 1909 Cambridge Darwin celebrations Balfourwas chosen to propose Darwin’s “immortal memory” at thebanquet on June 23. That morning the Chancellor, LordRayleigh, had ended his address of welcome to the delegatesby saying

During the last generation, Cambridge, especially sincethe time of Michael Foster, has been active in biologicalwork. We have the men and the ideas, but the difficulty hasalways been lack of funds. At the present time it is desired,among other things, to establish a Chair of Genetics – a sub-ject closely associated with the name of Darwin and of hisrelative Francis Galton, and of the greatest possible impor-tance, whether it be regarded from the purely scientific orfrom the practical side. I should like to think that the in-terest aroused by this Celebration would have a practicaloutcome in better provision for the future cultivation, in hisown University and that of his sons of the field whereinDarwin labored (Cambridge University Reporter 1908–1909, p. 1372).

The plea did not fall on deaf ears. In July 1910 Balfourwrote a short article dealing with the endowment of thestudy of Genetics in the University. Late in 1911 a meeting

was held at Balfour’s house in London, as a result of whichan anonymous benefactor placed in the hands of Balfour’sfriend Viscount Esher the sum of £20,000 to endow a Pro-fessorship to be called the Balfour Professorship of Genetics(Cambridge University Reporter 1911–1912, p. 694). Regu-lations were drawn up, which stipulated that the initial ap-pointment should be made by Balfour and the PrimeMinister jointly. It was also decided that the title should bethe Arthur Balfour Professorship to avoid confusion withFrancis Balfour.

Balfour wrote to Bateson, inviting him to accept theProfessorship, but Bateson, unwilling to return from hisDirectorship of the John Innes Institute, declined andsuggested that Punnett “is in every way worthy to beappointed” (Cock and Forsdyke 2008, p.386). And so hewas, on November 11, 1912, being formally admitted atthe Congregation on November 22. Whittingehame Lodge,the Professor’s house, was presented to the University in1914 by Viscount Esher and Arthur Balfour, by then an Earl.

Punnett’s legacy to Cambridge University as Professorwas modest. When his successor R. A. Fisher was electedin 1943, he found no staff and no students, but the largehouse, Whittingehame Lodge, intended for his occupation.“With the coming of war, the house was let to tenants andthe land plowed up by the War Agricultural Committee. Thedepartment ceased to exist” (Box 1978, p. 398). Fisher wasable to live in Caius College, since his Fellowship had beenrenewed on his return to Cambridge. Between 1943 and hisretirement in 1957 he used the house and garden to developa small Department and start a third-year Natural SciencesTripos subject, “Genetics.” Nowadays the Department thr-ives, and one valuable direct legacy of Punnett’s remainsto this day: his collection of offprints and many of his books.

However, Punnett influenced the young Fisher, who wasa student in Caius College in 1909–1913 during which timehe helped to found the Cambridge University Eugenics So-ciety, approaching Punnett, one of the dons who was a mem-ber of the national Society, to serve on its Council. Punnettgave a lecture at the second public meeting of the UniversitySociety on December 5, 1911. “The undergraduate commit-tee of the Society found Punnett’s exposition of Mendelismso important that, at a meeting in Fisher’s rooms [in Caius]the following term, Fisher as chairman proposed that theyshould make it a rule that each academic year one paperbe devoted to an elementary exposition of the principlesof heredity, meaning, of course, Mendelism” (Mazumdar1992, p. 99).

From 1920 to 1926 Fisher was a Fellow of Caius at thesame time as Punnett and though not resident he wouldhave met him frequently. It was Punnett who, with KarlPearson, reported unfavorably for the Royal Society onFisher’s (1918) famous article “The correlation between rel-atives on the supposition of Mendelian inheritance,”prompting Fisher to remark to W. F. Bodmer in 1956 “My1918 paper was refereed by Pearson and Punnett, both ofwhom I later succeeded” [personal communication; see also

10 A. W. F. Edwards

Fisher’s letter to C. S. Stock, November 18, 1943, replying toStock’s letter congratulating him on election to the ArthurBalfour Professorship (Bennett 1983, p. 264)]. All thingsconsidered, Fisher did not have a high academic opinionof his predecessor. I give some of the reasons for this below.Punnett had gone to his Somerset retirement before Fisherreturned to Caius, and although they overlapped as Fellowsuntil Fisher died in 1962, Punnett did not return often andthere is no corporate memory of their interaction when hedid.

Population Genetics

The story of Punnett’s friendship with the mathematician G.H. Hardy and how it led to Hardy’s 1908 discovery of “Hardy–Weinberg equilibrium” at the same time as W. Weinberg’s hasoften been told, not always correctly. In itself it reveals little ofPunnett except that he was puzzled by something that reallyis extremely simple, and he had to get Hardy to set himstraight. The fullest and, I hope, most accurate, account isto be found in a recent Perspectives (Edwards 2008).

Later, when writing his book Mimicry in Butterflies,Punnett (1915) appealed to Hardy for some more mathemat-ical help. He wanted to know the effects of selection at a singleMendelian diallelic locus under random mating, and Hardy,perhaps aware of the amount of computation involved, passedthe problem on to his Trinity pupil H. T. J. Norton. The resultswere published in tabular form in Appendix I of Punnett’s(1915) book (and reprinted in Provine 1971). They were veryinfluential, among other things inspiring J. B. S. Haldane toinitiate his long series of articles on selection. Haldane wasappointed Reader in Biochemistry at Cambridge in 1923, witha Fellowship of Trinity, and wrote that in 1922 Norton hadshown him some calculations that were eventually publishedin 1928 (Haldane 1927; Norton 1928). Provine (1971) maybe consulted for further details and Charlesworth (1980) fordetails of “Norton’s theorem.”

In 1917 Punnett again sought Hardy’s help over a similarproblem, and this time Hardy himself calculated how slowlya recessive lethal is eliminated from a population, thus ap-parently discrediting the eugenicists’ claim that deleteriousrecessives could be eliminated in a few generations (Punnett1917b). However, Fisher (1924) countered that these calcu-lations “have led to a widespread misapprehension of theeffectiveness of selection.”

Punnett (1930a) reviewed The Genetical Theory of Natu-ral Selection (Fisher 1930a) for Nature. It was not friendly.Fisher (1930b) replied in a letter to Nature, to which theeditor allowed Punnett (1930b) an immediate rejoinder. Wenow know, what Fisher could not have known at the time,exactly what Punnett reported to the Royal Society aboutFisher’s “1918” article (Norton and Pearson 1976): “I havehad another go at this paper but frankly I do not follow itowing to my ignorance of mathematics.” He ended “I do notfeel that this kind of work affects us biologists much atpresent. It is too much of the order of problem that deals

with weightless elephants upon frictionless surfaces, whereat the same time we are largely ignorant of the other prop-erties of the said elephants and surfaces.” It was not to beexpected that a man of such opinion would, only a dozenyears later, be able to offer an informed assessment of TheGenetical Theory, and Punnett seemed to admit as such:“Probably most geneticists to-day are somewhat skepticalas to the value of the mathematical treatment of their prob-lems. With the deepest respect, and even awe, for that as-sociation of complex symbols and human genius that canbring a universe to heel, they are nevertheless content tolet it stand at that, believing that in their own particular lineit is, after all, plodding that does it.” Leonard Darwin wroteto Fisher “I am rather sorry they picked out an old discon-tinuous stick-in-the-mud like Punnett to review you in Na-ture. But to get 5 columns is an excellent advertisement. Myfather would have been much pleased with such a review ofthe Origin, and merely carefully noted the points to answerin his next edition. I think you may be well pleased. I neverhad so long a review” (Bennett 1983, p. 131).

In the review Punnett advanced his mutationist position:“Throughout the book one gets the impression that Dr.Fisher views the evolutionary process as a very gradual,almost impalpable one, in spite of the discontinuous basisupon which it works.” He touches on melanic moths, onpoultry, and on mimicry, subjects on which he was well in-formed as a naturalist, and ends up by complaining aboutFisher’s English. Bennett (1983, p. 35) reports that the re-view “was a great disappointment to Fisher,” but one won-ders whether the disappointment was more over the choiceof reviewer than the content, because Fisher knew Punnettwell enough not to have expected anything else from him.Fisher’s response listed six points (“misstatements or otherslighter misrepresentations”), and Punnett attempted to an-swer them. The exchange served only to emphasize themagnitude of the scientific gulf that separated the first twoholders of the Arthur Balfour Professorship of Genetics.

Conclusion

Reginald Crundall Punnett owed his academic career andreputation to the good fortune of being invited by WilliamBateson to join him as his partner in undertaking breedingexperiments in both plants and animals in the heady daysthat followed the rediscovery and appreciation of Mendel’sarticle at the beginning of the 20th century. Having madea signal contribution to these studies his good fortune con-tinued when he found himself the natural alternative toBateson to occupy the Arthur Balfour Professorship of Ge-netics at Cambridge when Bateson declined it. Thereafter helived the comfortable life of a Professor between the wars,provided with a house by the University, a Fellowship by hisCollege, and the absence of pressing duties by either.

But one should not belittle the diagram that bears hisname, any more than one should belittle Venn’s famous logicdiagram, just because it is simple. It served a need so well that

Perspectives 11

it is difficult to see how the complex pattern of inheritance offlower color in the sweet pea could have been unraveledwithout it. The discovery of partial linkage depended on theknowledge thus gained. Bateson (1909, p. viii) wrote “In1904 I had the good fortune to gain Mr. R. C. Punnett asa partner. Since that date we have worked in close collabo-ration, and the work that we have thus done has been inevery sense a joint product, both as regards design, execution,and interpretation of results.” But he was careful to attributethe diagram to Punnett, as we have noted.

G. Evelyn Hutchinson (Hutchinson 1979) rememberedfrom his undergraduate days:

Genetics was taught twice a week, at five o’clock in theMichaelmas term, by R. C. Punnett . . . . He was a mild manwith an overdominant wife who had been a major tennisplayer. Her opponents must have been terrified. Punnetthad fine collections of Chinese porcelain and Japaneseprints in a delightful house backed by an experimentalgarden, and he devoted himself largely to the genetics ofsweet peas. The Punnetts gave Sunday lunches with superbwine to an incongruous set of students, half biologicalintellectuals, half athletes, all I think men. Only about halfa dozen students took Punnett’s course. . . . The chromo-some theory was still widely debated. Bateson was usuallyskeptical, though I know he accepted it for about a fortnightbefore his death. Punnett tended to be more receptive tothe idea. One evening the high point of the course arrivedunexpectedly; Punnett came in demurely and then an-nounced that he had just finished all the calculations oflinkage of the various characters he had studied in thesweet pea and that indeed there were as many linkagegroups as chromosomes. The chromosome theory hadworked for a plant as well as an animal and thereforemight reasonably be expected to be of general validity(Hutchinson 1979, p. 99).

Punnett’s paper reporting this is Punnett (1923b).But I leave the last word to Joseph Needham (Needham

1967), the Master of Caius: “Punnett also had a highly schol-arly side, being greatly interested in the history of biology andpossessing a notable library of its seventeenth and eighteenth-century literature. Unfailingly helpful and charming to youn-ger colleagues, he would present them sometimes with rarebooks, and encourage them in their work in ways which theycould never hope to repay. We greatly cherish his memory andrecord this for the information of later generations.”

Acknowledgments

I am grateful to Peter O’Donald for the reference to Hutch-inson (1979) and to Axel Zeitler for help in understandingCorrens (1900).

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Perspectives 13