A NEW BRANCHIATE OLIGOOH^TK. 325

A New Branchiate Oligochsete (BranchiuraSowerbyi).

By

Frank E. Beddard, M.A.,Prosector to the Zoological Society of London, Lecturer on Biology at

Guy's Hospital.

With Plate XIX.

W E are acquainted at present with three genera of Oligo-chaeta which render the Cuvierian name of " Anne'lidesabranches se'tigeres" no longer applicable to the group.Dero has been known since the time of Rosel and Otto Fried-erich Mtiller, the latter of whom recognised the branchial func-tion of the ciliated processes at the anal extremity of the body.Alma nilotica, originally described by Grube,1 and latelyreinvestigated by Levinsen,2 is, according to Grube, much likea Rhynchelmis in general habit. It has paired sigmoidsetae; the posterior sixty segments or so are furnished withshort dorsally placed processes, more numerous upon the an-terior than the posterior of these segments. The name givenby Levinsen is Dig i t ib ranchus n i lo t i cus ; but this wormis, in all probability, generically and specifically identical withAlma nilotica. The third branchiate form has been quitelately described in this Journal3 by Professor A. G. Bourne.

1 "Beschreibungen neuer oder wenig bekannter Anneliden," 'Arch. f.Naturg.,' 1855, p. 129.

2 "Om to Regnormslaegter fra .̂ Bgypten," 'Vidensk. Meddel. naturk.Foren.,' 1859, p. 321.

a "On Chsetobranchus, a New Genus of Oligocheetous Chsetopoda,"'Quart. Journ. Micr. Sci.,' vol. xxxi, p. 83.

VOL. XXXIII, PART III. NEW SEE. Z

326 tfRANK t. BBDDARD.

It is a Naid furnished with long processes on the anterior seg-ments which lodge the dorsal setae. I shall refer more par-ticularly to the structure of these processes in describing aquite new type of branchiate Oligochsetous Annelid which Ipropose to name.

Branchiura Sowerbyi, nov. gen. et sp.In looking over some mud from the " Victoria regia tank "

in the Royal Botanical Society's Gardens, Regent's Park, Ifound three specimens of an Annelid which struck me at onceas probably new. It was remarkable for the unusual con-tractility of the body, which suggested a leech or a flat-wormrather than a Chsetopod. For this reason it is impossible togive any accurate measurement; half an inch to three quartersis about its length. It consists of about 120 segments (therewere 170 in the largest individual). Examined with a lens,the orange-coloured digestive tract traversed by the brightblood-vessels could be seen ; and at the posterior end ofthe body a series of delicate dorsal and ventral pro-cesses. The position of these organs, which I shall presentlygive reasons for believing to be branchiae, suggested the genericname; the species I have great pleasure in associating withthe name of Mr. Sowerby, of the Botanical Society.

After carefully noting and sketching the principal features ofthe worm when examined alive under low and high powers ofthe microscope, 1 preserved one specimen with corrosive subli-mate and acetic acid, followed by gradually increasing strengthof alcohol; the others with Perenyi's solution—a much betterreagent—for histological study.

§ Branchiae.

The principal structure of interest in this worm is of coursethe series of branchial processes. These are apparent, whenthe worm is examined with a lens, as a delicate fringe whichdecks the last one sixth or one seventh of the body, giving it afeather-like appearance. There are altogether about fiftypairs of these processes, which are segmentally arranged, i. e.

A NEW BRANCHIATE OLIQOOHJITB. 327

one pair to each segment. In the largest of the three wormsthere were at least eighty of these processes on each side. Here,again, I am unable to be absolutely accurate; the processesfirst appear as mere mammillary outgrowths, which graduallyincrease in length upon successive segments; it is difficult,therefore, to say exactly when they begin. From being theslightest elevations, barely perceptible, of the integument, theprocesses become nearly as long or even longer than the dia-meter of the worm's body: they then gradually diminish inlength towards the anus; but they are not so small at thefinish as at the beginning, nor are there so many rudimentarybranchiae at the anal end of the series as there are at the oralend. In one specimen, with only twenty pairs of branchiae, therewere no rudimentary ones at the posterior end of the series.

By a remarkably fortunate accident, the water which pro-duced the specimens of Branchiura Sowerbyi containedalso tbtee or four examples of Bourne's Chaetobranchus. Ihave, therefore, been able to compare the two forms, detail fordetail, though I have convinced myself that Bourne's excellentdescription really rendered an examination of the worm Chae-tobranchus itself unnecessary.

The first important difference, then, between the branchialprocesses is a difference in position. In Chaetobranchusthe branchise are anterior, g radua l ly d iminishing andfinally d isappear ing p o s t e r i o r l y ; in Branchiurathey are developed upon the last sixty segments ofthe body or so.

In examining the living Chaetobranchus it is easy to seethat, as Bourne has described and figured, the setae are con-tained within the branchiae. The long capilliform seta of thedorsal bundles reaches nearly to the end of the branchia. InBranch iu ra there is no connection at all between the bran-chial processes and the setae. The branchiae are, in fact, notlatero-dorsal in position, as in Chaetobranchus; they arisefrom the body-wall dorsally and ventrally in the middle line.

In the figure which illustrates the living worm (fig. 2) theanus is shown to one side of the body apparently ; the worms

328 FRANK B. BBDDABD.

were nearly always in this position when examined alive. Ihave found, however, by transverse sections, that the bran-chial process arises in the middle dorsal and middleventra l l ines of the body respectively. This is shownin the sections represented in fig. 13. The anus is thusreally dorsal, as in Dero, and there is nothing especially ab-normal about its position. But the position of the branchiaeis very remarkable indeed; a fusion between the branchiae ofsuccessive segments would produce something like the un-paired fins of Vertebrates. It has been suggested, by theadvocates of the Annelid origin of Vertebrates, that the ap-proximation and fusion in the mid-dorsal line of the notopodiaof the parapodia may have produced the dorsal unpaired fin;in Branchiura we have the unpaired character of the pro-cesses of the body already established.

When Chsetobranchus is in motion the branchial pro-cesses naturally move with the setae; there is, so far as I couldascertain, no intrinsic movements of the branchiae themselves,which indeed do not appear to be provided with any muscles,as Professor Bourne has rightly stated. They are kept rigidby the setse. In Branchiura the individual movement ofeach branchia can be readily seen. The whole of the posteriorend of the worm's body was in continual movement, while theanterior end remained quiet. The body itself oscillated toand fro with a peculiar vibratory movement: this of itselfcaused a fluttering of the branchiae; but in addition to thiseach branchia moved independently, writhing about like thecirri and tentacles of some Polychseta. The branchiae not onlymoved from side to side, but became alternately extended andretracted, so that their length was much greater at one timethan at another. Hence it is difficult to give any measure-ment that would apply accurately to the branchiae of the livingworm. After treatment with corrosive sublimate and alcoholthe length of the longest branchia was generally rather lessthan the diameter of the body; during life it was frequentlythe other way about. The branchiae frequently present thewrinkled appearance shown in the accompanying figure (PI.

A NEW BRANCHIATE OLIGO0H.ETE. 329

XIX, fig. 5); this is of course due to the contraction. Themovements of the branchiae are effected by muscular fibreswhich run across the cavity of the branchia from side to side;these fibres are elongated, fusiform, with a central nucleus.They are sometimes branched, forming star-shaped bodies withthe nucleus in the centre.

The structure of the branchiae (see fig. 6) is very simple; theyare covered by a firm cuticle, beneath which lies the epidermis.Bourne detected fine vibratile cilia upon the branchiae ofChaetobranchus. I failed to discover any cilia upon thebranchiae of Branch iura . The axis of the branchia is occu-pied by a cavity evidently belonging to the coelom ; imme-diately beneath the epidermis is a layer of muscles whichappears to be continuous with the circular layer of the body-wall; beneath this is the peritoneum. In Chsetobranchusthere is a capillary loop running up the branchiae in the ccelom,which in that worm, as in Branchiura , is prolonged into thebranchiae. In Branchiura there is no such capillary looplying freely within the cavity of the branchia, but immediatelybeneath the epidermis is a blood-vessel on each side whichgives a yellowish or even red colour to the branchia whenexamined under the microscope. I shall speak further of theblood-supply of the branchiae in considering the course of theblood-vessels.

Although the branchiae have an axial cavity, traversed bythe muscular fibres which cause the contractions of the branchiaeand lined with peritoneum, this cavity is not actually in com-munication with the body-cavity ; in the living worm the cavityof the branchia can be easily seen to be shut off from thecoelom by a diaphragm which moves synchronously with thecontractions of the dorsal vessel. It becomes alternately convexand concave outwards : when convex, i. e. when forced forwardsby the liquid of the coelom, it projects some way into theinterior of the branchia, and is very conspicuous ; it appearedto me to completely block all ingress of solid matter into thelumen of the branchia. The coelom of this worm contained nofreely floating corpuscles that 1 could discover; I am not able

330 PRANK B. BBDDARD.

to make a definite assertion upon the matter. But in one speci-men the cavity of the branchia contained a quantity of oval orfusiform bodies (fig. 11), of problematical nature. These movedto and fro with the contractions of the branchiae, but I foundnone in the body, nor did I ever see them pass the diaphragm.

In the above account of the branchial organs I have com-pared them with those of Chaetobranchus. The importantdifferences lie in the position, the contractility, and the inde-pendence from the setae of the branchiae in Branchiura. Thefact that in Chaetobranchus the setae are embedded in thebranchiae suggests a comparison with the parapodia of PolychaeteAnnelids; but it must be remembered that the enclosure ofthe setae within the branchial processes of Chaetobranchusappears to be secondary. They are at first, partially at least,unenclosed by the branchiae. In Branchiura the branchiaerecall the simpler forms of gills in certain Chaetopods, perhapsalso the cirri. I am not, however, disposed to lay any stressupon these resemblances, apart altogether from the wide separa-tion between the existing Polychaeta and Oligochaeta; it isquite intelligible that structures of this kind may have arisenindependently. Indeed, I am of opinion that there is nogenetic connection between the branchiae of even the fourOligochaetous genera now known to possess these organs, viz.Dero, Alma, Chaetobranchus, and Branchiura . ThoughDero and Chaetobranchus are probably both Naids, theirbranchiae are too different in structure and position to admitof a direct homologisation without further facts than thoseknown. Branchiura I believe to be a Tubificid, and itsbranchiae are again different. Alma cannot at present becertainly regarded as an Oligochaete at all;1 if it is, I aminclined to regard its branchiae as more like those of Bran-chiura than those of either Dero or Chaetobranchus.

1 Its resemblances to such a Capitellid as Mastobranohus have beenpointed out; but Eisig (' Monograph der Capitelliden'), though admittingthese resemblances, leans to the opinion that it is an Oligochsete, on accountof the blood-vessels described by Grube. There are, of course, no blood-vessels in the Capitellidse.

A NEW BRANCHIATE OLIGO0HJ3TE. 331

The remaining external characters of Branchiura are ofless importance. The prostomium is conical, short, androunded in front (see fig. 4). Each of the anterior segmentsis bi&nnulate, as in many Tubificidse. The dorsal setabundles alone contain capilliform setae, and there are at themost two of these to a bundle. The other setse of the dorsalbundles are "crotchet-shaped." Very frequently the upperfork is worn away, so that the setse resemble those of certainLumbriculidse, and appear to be simple sigmoid setse, unnotchedat the extremity. The ventral setae are of one kind only—" crotchet-shaped." There is no " cephalisation " shown bythe setse. The second segment of the body has both dorsaland ventral bundles. The first two pairs of bundles, however,sometimes have no capilliform setas, but this is probably acci-dental or an individual peculiarity, since in a second specimenthey were present. The number of short setse in the dorsalbundles of the first twenty segments or so is four to six,generally five; but generally six or seven in the larger speci-men. Further back the number of these setse in each bundleis less, being two or three. In the dorsal bundles of the mostposterior segments there seem to be no capilliform setae. Inthis the worm resembles Tubifex.

§ Vascular System.I studied the vascular system principally in the living

worms, but also by following out the course of the vessels intransverse and longitudinal sections. The blood was dis-tinctly red in the larger vessels. The only contractile trunksare the dorsal vessel and certain of the circumoesophageal ringswhich connect it with the ventral vessel. The pulsations ofthe dorsal vessel pass from behind forwards, of the " hearts "from above downwards. Both the dorsal and ventral blood-vessels run from end to end of the body. It is remarkable thatthe term " dorsal" vessel1 is quite inapplicable to the longi-

1 It is curious to learn from Eisen ("Preliminary Report on Genera andSpecies of Tubiatidas," 'Bik. K. Svensk. Ak. Handl.,' Bd. iv, p. 7) thatsomething of the same kind occurs in Telmatodrilua, though reversed;

332 FRANK B. BBDDABD.

tudinal contractile vascular trunk \ it is only in the oesophagealregion that it is upon the upper surface of the alimentary tract.Further back it runs in close contiguity to the ventral blood-vessel, so close that at first I was disposed to regard this wormas resembling certain Polychseta in having a double ventralblood-vessel. It is very easy to see, however, that the twotrunks do not always run side by side (they do in the branchialregion), and that one only is contractile. In addition to thesethere is a supra-intestinal vessel, which I was only able torecognise in the living worm, upon the oesophagus and just thebeginning of the intestine, but in sections I traced it furtherback ; it lies beneath the peritoneal covering of the alimentarytract, while both the dorsal and ventral vessels lie freely in thebody-cavity, and the former, like the latter, has no covering ofpigmented cells. The figure (fig. 10) illustrates the course ofthe principal blood-vessels so far as I was able to make themout. I am not certain about the connection of the dorsal andventral trunks in the most anterior segments. In longitudinalsections the close proximity of the dorsal and ventral vesselscould be easy made out; the latter rests upon the nerve-cord.In each segment of the body after the hearts there seem to betwo peri-intestinal vessels ; one runs in the septum, the other atabout the level of the setse; but I did not make out their con-nection in a satisfactory way.

In the section illustrated in fig. 13 the relations of the dorsaland ventral vessels in the branchial region of the body and theblood-supply of the branchiae can be made out—at least partly.The body appears something like the fig. 8 in section, but thiswas not always the case. In those sections which exhibitedthe figure-of-eight outline the upper cavity was exclusivelyoccupied by the intestine, the lower cavity by the nervoussystem and the principal blood-vessels. The intestine is attachedto the parietes by numerous muscular strands, and thereappears always to be a partition1 (at sp. in the fig.) which shutsthe ventral trunk lies towards tbe dorsal side of the body. In Dero thedorsal vessel is ventral in position.

1 Among the Gapitellidte and other Polychseta the coelom is similarlydivided.

A NEW BEANOHIATE OLIGOCHJOTE. 333

off the upper part of the ccelom from the lower part, and whichcorresponds to the " waist" of the figure of eight. There isnothing particularly noteworthy about the structure of thebody-wall. The longitudinal muscular layer (/. m.) consists ofa single layer of flat plates, the interstices between which areoccupied by a granular nucleated substance which also forms athickish layer on the inside of the muscles. Where thebranchiae arise the muscular layer is interrupted. The lowercompartment of the ccelom is occupied, as already stated, by thenerve-cord and the blood-vessels. The ventral blood-vessel canbe easily distinguished from the dorsal, not by its position, forthey both lie side by side, but by the structure. The pulsatingdorsal vessel has thicker muscular walls and much less bloodin the lumen; the blood in this vessel was never so darklystained by the carmine as the blood in the ventral vessel. Ido not understand this unless it be that the muscular walls areparticularly impermeable to that fluid. The dorsal vessel lieson the left side just above the nerve-cord, and when fully ex-panded is of about the same calibre as the ventral vessel. Inparts, however, its lumen was so contracted that the vesselcould only with difficulty be recognised. The ventral vesselhas very thin walls, and was gorged with blood. It gives off(see fig. 13) a branch on the right side which immediatelydivides into two—a branch for each of the branchiae. Thebranches run up and down the body close to the parietes andenter the branchiae: the efferent branch passes down the oppositeside of the body-wall in a corresponding position, but I did notsucceed in seeing its actual opening into the dorsal vessel—presuming always that such an opening exists ; but at the pointswhere these vessels should open it always happened that thedorsal vessel was much contracted, while the end of the efferentbranchial vessel was much dilated. This looks as if the flowof blood into the dorsal vessel was hindered at the moment ofdeath by the contraction of the latter obliterating its lumen,and thus rendering the actual communication so slender as toescape attention.

Another important point with regard to the circulatory organs

334 PRANK E. BEDDARD.

of this Oligochsete is the presence of an extensive integumentalnetwork of capillaries. These consist of a large number oflongitudinal trunks united by transverse vessels so as to con-stitute a network. A portion of this network is illustrated infig. 7, which figure also shows the branchial loops: thebranchial loops are not connected with the network shown inthe figure.

The aquatic Oligochseta are, as a rule, not provided with anintegumental blood-plexus; indeed, until recently the absenceof such would be considered to distinguish the earthwormsfrom the limicolous Oligocheeta. Nevertheless I lyodri lusappears, from the figures given by Stole/ to possess an integu-mental vascular plexus which seems to be as fully developed asin Branchiura. In the small tract of body-wall illustratedin fig. 7 I observed at least three longitudinal trunks.

In the anterior part of the body, at any rate, the vascularnetwork arises from paired trunks, which take origin from thesupra-intestinal blood-vessel (see fig. 9).

The existence of an integumental network is, as has beenalready mentioned, a rare occurrence among the aquatic Oligo-chseta ; the interest attaching to its existence in Branch iu rais increased by the fact that the worm possesses special branchialorgans. In about seven or eight of the anterior segments twoof the longitudinal trunks of the integumental network areparticularly enlarged, and in one specimen, at any rate, werevery conspicuous j they run, as shown in the figure (fig. 9,L. V.), on either side of the nerve-cord, but below the ventralblood-vessel. I have not attempted to represent their branch-ing, which is, I believe, connected with the system of vesselsderived from the supra-intestinal blood-trunk.

I regard these vessels as the homologues of the " intestino-tegumentary" trunks of earthworms; their presence inBranchiura removes another structural barrier between the" Terricolse" and " Limicolse" of Clapare'de.

Finally, with regard to the circulatory system, I have tomention the existence of a pair of intestinal hearts; they lie in> "Monografie Cesk/ch Tubiflcidu," ' Abh, Bohm. Ges,/ 1888, pi, ii, fig. 3,

A NEW BRANCHIATE 0LIG00H2ETE. 335

the 8th segment (fig. 9, H'.), and connect the supra-oesophagealwith the ventral blood-vessel. They appear not to be con-tractile, and coexist in the 8th segment with the usual pair ofcontractile hearts. In each segment of the body in this regionthere is, as has been mentioned, a pair of vessels given off fromthe supra-intestinal trunk at about the middle of the segment,which join the integumental network. In the 8th segment acorresponding pair of vessels are present, which arise from theintestinal hearts.

The existence not only of a supra-intestinal vessel, but ofintestinal hearts connecting it with the ventral vessel, was un-known among the Limicolse until the publication of Stoic'simportant work upon the Bohemian Tubificidse. Such heartsexist in the genera Bo th r ioneuron and Lophochseta. Ihave also described an " intestinal" heart in the remarkablefresh-Water Oligochaete Phreodr i lus , 1 which appears to bethe representative of a distinct family, though showing somepoints of resemblance to the Tubificidae.

§ Nephr id ia , Al imentary Tract , &c.The perivisceral cavity appears to contain no free cor-

puscles. The anterior septa are thicker than the following ones.The nephr id ia are constructed on the same plan as in

Tubifex. The first pair were in the 12th segment. Thenephridium communicates with the exterior by a pear-shapedvesicle (see fig. 14), dilated where it receives the excretorytubule and gradually narrowing towards the external orifice,which is very small and placed in front of the ventral setabundle, at a point corresponding to about the middle of eachbundle.

The a l imentary t r ac t is like that of Tubifex. Thebuccal Cavity alone is not ciliated; the rest of the tube lyingbehind the buccal cavity is ciliated.

The oesophagus only differs from the intestine, which com-mences in the 11th segment, by its smaller calibre; it is much

1 " On Two New Genera of Aquatic Oligochreta," ' Trans, Roy. Soc. Edin.,'vol. xxxvi,

336 PRANK E. BEDDABD.

longer than in Tubifex, therefore : the brown peritoneal cellscommence in the 6th segment. There are septal glandspresent, which lie in Segments 4, 5, and 6. The intestine isattached to the parietes by muscular bands.

§ Genera t ive Organs.

In worms not sexually mature, two pairs of gonads inan immature condition were to be seen (in longitudinal sec-tions) in Segments 10 and 11. I presume that these are thetestes and ovaries, though there was no means of tellingtheir nature from their structure. In another specimen whichhad advanced a little, but not much, further towards maturitythe gonads were bigger, and stretched right across the seg-ment, and their nature (testis and ovary) could be establishedfrom their minute structure, but there was no trace of ducts orof sperrnathecse.

After examining five or six specimens of Branch iu rawhich were sexually immature, I was so fortunate as to dis-cover a single specimen with fully developed sexual organs.This individual was very much longer than the others, therelative size being shown in the figure (fig. 1, A, B). It wasan inch and a half to two inches in length. The presence ofthe sexual organs gave a milky-white appearance to some ofthe anterior segments. This was chiefly owing to the sperm-sacs.

With regard to the external differences produced by thedevelopment of the sexual organs I may direct attention tofig. 8. The cl i tel lum occupies three segments (10 to 12).The epidermis covering this region of the body is deeper thanelsewhere, but still, as in aquatic Oligochseta, consists of onelayer of cells only.

On to the 10th segment open the spermathecas. Thepaired apertures are situated behind the ventral seta bundles.

The a t r ia l pores are upon Segment 11. They correspondin position to the spermathecal pores, but lie where the ventralsetae would be were these present. The ventral setae of Seg-

A NEW BRANCHIATE OLIGOORffiTE. 337

ment 11 are totally absent, nor are they replaced by penialsetae.

Between Segments 11/12 are trie oviducal pores. On the12th segment the first pair of nephridiopores are to be seen, asalready mentioned.

With regard to the internal parts of the generative system,the position of the testes and ovaries has been already men-tioned.

The sperm-sacs are very greatly developed; they extendfrom the 9th to the 17th segment; they lie dorsally as well ason both sides of the intestine.

The spe rm-duc t opens by a large funnel on each side intothe interior of the 10th segment; the sperm-duct is compara-tively short, and after a few windings opens, as shown in fig. 12,into a straightish tube which leads to the exterior. In thatfignre the relations of the different parts of the whole efferentapparatus are shown ; the whole apparatus differs in manypoints from the corresponding organs of other Tubificidse. Thereis a large sac (fig. 1, At.) on each side of the body in the 11thsegment; this has a somewhat oval contour, and presents thehistological structure indicated in the figure. The lumen is nar-row, and lined with a single layer of epithelial cells, which hasbeen hardly at all stained by the borax carmine; they are clearin appearance, and their nuclei are pushed back to the base ofthe cell: this seems to indicate that the cells are in full secre-tory activity. Outside of this epithelial lining is a layer ofmuscular fibres about equal in thickness to the epithelium, thefibres of which are mostly arranged in a circular direction.This muscular layer is covered by a very thick layer of cells,five or six deep, which seem to represent a very much thickenedperitoneal coating.

This sac has a structure which evidently corresponds to thatof the atrium of other Oligochseta, particularly of R h y n c h e l -mis 1 and Moniligaster ,2 and more particularly of the latter;

1 VEJDOVSKY, " Anatomische Studien an Rynchelmis Limosella, &c,"• Zeifc. wise. Zool.,' Bd. xxvii, Taf. xxiv, fig. 1.

2 BEDD^BD, " On the Structure of Three New Species of Earthworms, &c,"Quart. Jouru. Micr. Sci.,' vol. xxix, pi. xii, fig. 11.

338 FRANK E. BEDDAftD.

but in Branchiura , instead of receiving the vas deferens, asit does in the two genera mentioned, this organ forms a diver-ticulum of the vas deferens. The difference is in fact preciselyanalogous to that which exists between Eudr i lus and Ponto-dri lus . A tubular gland exists in both: in Eudr i lus thevasa deferentia open into i t ; in Pontodr i lus they open at itsbase into a duct leading from it. In the latter case there is novalid reason against regarding the two structures as homologous,and I am of opinion that the glandular sacs of Branch iurawhich have just been described represent a portion of theatrium. This glandular section of the atrium passes abruptlyinto a narrow tube (a in fig. 1), which receives the sperm-duct just at its commencement: the sperm-duct becomes ex-ceedingly narrow just before it opens into this tube, which,like the sperm-duct, is ciliated. The distal part of the atrium,at first ciliated, loses the cilia further down, and the characterof the lining epithelium abruptly changes: the cells becometaller, and the cellular membrane as a whole is thrown intofolds. Both regions of the tube are enveloped by a thick mus-cular coat, but the most distal portion is probably protrusible,since it is surrounded by a space, which is, I think, as inTubifex, &c, lined by epithelium. The male efferent appa-ratus of Branchiura differs, therefore, in a number of pointsfrom the corresponding structures of other Tubificidse. Thedivision of the. atrium into two parts is commonly seen in theTubificidse, and is particularly well marked in Bothrio-neuron Vejdovskyanum,1 but in no Tubifex is the glandu-lar part so greatly developed, nor is there any other genus inwhich the vas deferens joins the muscular part of the atrium,thus making the glandular part into a caecum. This particularrelation of the two parts of the atrium to the vas deferens iscommon among earthworms.

The spermathecae lie in Segment 10. They are more orless pear-shaped, narrowing towards the external opening.They have no caeca or glandular appendages of any kind.They contained spermatozoa not aggregated into bundles.

1 Stole, loo. cit., Taf. iv, fig. 7, ichv and at.

A NEW BRANCHIATE OLtSOOHJiTE. 33§

The ovaries, as already mentioned, lie in the 11th segment.In the sexually mature worm I found masses of developingova in Segments 12 and 13 ; in the latter segment they were inclose contact with the sperm-sacs, and appeared to be enve-loped in a common sheath. In Segments 18 and 19 were twoor three fully mature ova, which, as in most aquatic worms, areof large size, and are filled with spherical yolk bodies.

For a long time the existence of oviducts in the Tubificidsewas unknown, and the ova were believed to leave the body insome way through the penis sheath. These structures werefirst found by Stole in I lyodr i lus and Psammoryctes , andsubsequently by myself in Cl i te l l io and Hemitubifex. 1 Ihave found them in Branchiura , where they are of preciselythe same structure as in other Tubificidse.

Affinities.

It will be apparent from the above account that Bran-chiura must be referred to the Tubificidaej of which family,however, it forms a very distinct new genus. It is difficult tosay to which of the remaining genera of the family it comesnearest; it is, indeed, nearly equally remote from all. The ab-sence of prostates (" Cementdriisen "), as well as the presenceof the integumental network of blood-vessels, perhaps bringsBranchiura into nearer proximity to I lyodri lus than to anyother Tubificidse. Stole has shown how I lyodri lus connectsthe Tubificidse with the Naidomorpha; but the relationship ofthe Tubificidse with the higher forms is not yet clear. I maypoint out, therefore, that the glandular part of the atrium inBranchiura shows in its structure a certain amount of re-semblance to that of the Lumbriculidse (Rhynchelmis), andto that of the simply organised earthworm Moniligaster.Its relations to the vas deferens are unlike what occurs in anyof the lower Oligochseta, but are paralleled in many earth-worms (e.g. Pontodri lus , Cryptodri lus) .

It is impossible at present to distinguish generic from• " On Certain Points in the Structure of Clitellio " (Claparede),' Proc.

Zool. Soc.,' 1888, p. 485.

340 FEANK B. BEDDABD.

specific characters, and so the following attempt at genericand specific definition must be regarded as only tentative.

BRANCHIURA, nov. gen.

Hinder 50—80 segments furnished with a series of branchialprocesses, a pair to each segment, arising one from the dorsaland one from the ventral median lines. Seta? capilliforin anduncinate, the former kind only found in the dorsal bundlesof the anterior segments. An integumental capillary plexuspresent. Atria consisting of a large oval sac enveloped, asin Lumbriculidse, by a thick layer of peritoneal cells, and of anarrow tube leading to exterior; vas deferens opens at junctionof glandular and non-glandular part of atrium.

Branchiura Sowerbyi, n. sp.Two pairs of specially dilated hearts in Segments 9, 10.

Intestine begins in 11 ; pigmented peritoneal cells appear firstin Segment 6.

EXPLANATION OF PLATE XIX,

Illustrating Mr. Frank E. Beddard's paper on " A NewBranchiate Oligochsete (Branchiura Sowerbyi)."

FIG. 1.—Branchiura Sowerbyi, nat. size. A. Larger (sexual) indivi-dual. B. Smaller individual, representing the average size.

FIG. 2.—Branchiura Sowerbyi, an individual slightly magnified.FIG. 3.—Seta of dorsal bundle, a. Capilliform seta. b. Uncinate seta.

c. Sigmoid seta;.

FIG. 4.—Prostomium and three anterior segments.FIG. 5.—Branchiae, showing transverse wrinkles due to contraction. Br.

Dorsal series. 2?/. Ventral series.

Fia. 6.—A single branchia, showing details of structure, c. Cuticle.Ep. Epidermis, beneath which lies blood-capillary. M. Muscular fibrilsstretching across lumen. 1). "Diaphragm."

A NEW BRANCHIATE OLIGOOHfllTE. 341

FIG. 7.—A part of integumental network of posterior segments. Br.Branchia. Int. Intestine.

FIG, 8.—Ventral external view of Segments 9—14. el. Clitellum. s. Ven-tral seta bundles. Sp. Spermathecal pores. <?. Atrial pores. ? . Oviducalpores, np. Nephridiopores.

FIG. 9.—Diagram to illustrate principal blood-vessels of Segment 8. al.Alimentary canal. N. Nerve-cord. D. V. Dorsal vessel. V. V. Ventralvessel. H. Contractile heart. S. i. V. Supra-intestinal vessel. H'. Intestinalheart, giving off on each side a vessel which joins the integumental network.L. V. Lateral vessels connected with integumental network.

FIG. 10.—Principal trunks of vascular system in anterior region of body.Lettering as in Fig. 9.

FIG. 11.—Corpuscles from axial cavity of branchia.FIG. 12.—Male efferent apparatus. F. Funnel of vas deferens. Vd. Vas

deferens. X. Junction of vas deferens with atrium {Al.). Cav. Cavity ofatrium. Vd'. Coils of vas deferens lying behind atrium, a. Ciliated thin-walled tube leading from atrium to b, protrusible penis, separated by a spacefrom its muscular sheath.

FIG. 13.—Transverse section through body in branchial region. Br. d.Dorsal branchia. Br. v. Ventral branchia. Int. Intestine. N. Nerve-cord, sp. Septum separating dorsal from ventral part of ccelom. D. V.Dorsal vessel. V. V. Ventral vessel; the latter gives off a branch, whichimmediately divides to supply dorsal and ventral branchiae.

FIG. 14.—Extenal opening of nephridium through a dilated vesicle (JV.).*. Ventral seta.

FIG. 15.—Longitudinal section through head, to show position of brain,which lies in prostomium and first segment of the body.

VOL. XXXIII, PART III. NEW SEE.

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