selecc thompson_on growth and form

8/12/2019 Selecc Thompson_on Growth and Form

1/7


2/7

OF

THE

SIZE

OF CELLS

61

the

leaf-cells

are

found

to be

of

the

same

size in an

ordinary

water-

lily,

in

the

great

Victoria

regia,

and

in

the still

hiiger leaf,

nearly

3

metres

long, of

Euryale

ferox

in

Japan*.

Driesch

has

laid

par-

ticular

stress

upon

this

principle

of

a

fixed

cell-size,

which

has,

however,

its

own limitations

and

exceptions.

Among these

excep-

tions,

or

apparent exceptions, are the

giant frond-like

cell of

a

Caulerpa

or

the great

undivided

plasmodium

of a

Myxomycete.

The flattening

of

the

one and the

branching of

the

other

serve

or

help) to

increase the ratio

of

surface

to

content, the

nuclei tend

to

multiply,

and streaming

currents

keep

the

interior

and

exterior

of

the

mass

in

touch with one

another.

j^

Rabbit

Man

Dog

Fig.

3.

Motor

ganglion-cells,

from the

cervical spinal

cord.

From

Minot,

after Irving

Hardesty.

We

get a

good and

even

a

famiUar

illustration

of

the principle

of

size-hmitation

in

comparing

the

brain-cells

or

ganghon-cells,

whether

of

the

lower or

of

the higher

animals

f

.

In Fig. 3 we shew

certain

identical

nerve-cells

from

various

mammals,

from

mouse

to

elephant,

all

drawn

to

the

same

scale

of

magnification

;

and

we

see

that

they

are

all

of

much the

same

order

of

magnitude. The

nerve-

cell

of

the elephant

is

about

twice

that

of the

mouse

in linear

sluggish

Amphibia are

much

the

largest known

to

us,

while

the

smallest are found

among the deer

and

other

agile

and

speedy

animals cf.

Gulliver, P.Z.S.

1875,

p.

474,

etc.). This

correlation

is explained

by

the

surface

condensation

or

adsorption

of

oxygen

in

the

blood-corpuscles,

a

process

greatly

facilitated

and

intensified

by

the increase

of

surface

due

to their

minuteness.

*

Okada and

Yomosuke,

in

Sci. Rep.

Tohoku

Univ. iii,

pp.

271-278,

1928.

t

Cf. P. Enriques,

La forma eome

funzione

della

grandezza

:

Ricerche

sui

gangli

nervosi

degli

invertebrati,

Arch. f.

Entw.

Mech.

xxv,

p.

655,

1907-8.


3/7

VIII]

OF SPORES

AND

POLLEN

631

fail

to assume,

even

temporarily,

the tetrahedral form:

cases,

in

a

general

way,

where

the four

cells

escape

from

the

confinement

of

their

envelope,

and fall

into

a

looser,

less

close-packed

arrangement*.

The

figures

given

by

Goebel

of the development

of

the

pollen*

of

Neottia

(3,

a-e\ all the

figures referring

to grains

taken

from

a

single

anther)

illustrate this

to perfection,

and

it

will

be seen

that,

Fig.

278.

Various

pollen-grains

and

spores

(after

Berthold,

Campbell,

Goebe

and

others).

(1)

Epilobium;

(2)

Passiflora;

(3)

Neottia;

(4)

Periploca

graeca;

(5)

Apocynum;

(6)

Erica;

(7)

spore

of

Osmuyida;

(8)

tetraspore

of

CnUithavinion.

Fig. 271).

I ollon

of

bulrush

(Tifpha).

After

Wodehouse.

when

the

four

cells lie

in

a

plane,

they

conform

exactly

to our

typical

diagram

of

the

first

four

.cells

in

a

segmenting ovum;

physically,

as

well

as

biologically,

the

tetrads

a-d

and

the tetrad

e

are

allelomorphs

of one

another.

Again

in

the

bulrush

(Fig.

279),

*

Cf.

C.

Nageli, Znr

Entwickhingsgeschichte

des

Pollens

bei

den Phanerogamen,

36

pp.,

Zurich,

1842;

Hugo

Fischer,

Vergleichende

Morphologie

der Pollenkorner,

Berlin,

1890;

see also,

for

many

and

varied

illustrations,

R.

P.

Wodehouse s

beautiful

book on

Pollen,

574

pp..

New

York,

193o,

and

earlier

papers.


4/7

VI]

OF

MORPHOLOGICAL

POLARITY

455

of

linear

arrangements of

particles,

which

in

the

elongated

or

monopolar

cell

run

parallel

with

its

axis,

but

tend

to

a radial

arrangement

in

the

more

or

less

rounded or

spherical cell. Of

late

years

great

importance

has

been

attached

to

these various

linear

or

fibrillar

arrangements,

as they are seen

(after

staining)

in

the

cell-

substance

of

intestinal

epithelium,

of

spermatocytes,

of

ganglion

cells,

and

most abundantly and

frequently

of all

in

gland

cells.

Various

functions

have

been

assigned,

and

hard

names given

to

them;

for

these

structures

include your

mitochondria* and

your

chondriokonts (both of

these being

varieties

of chondriosomes),

your

Altmann s

granules,

your

microsomes,

pseudo-chromosomes,

epi-

M^m.

Ih

A

B

C

Fig.

149. A, B,

Chondriosomes

in kidney-

cells,

prior

to

and

during

secretory

activity (after Barratt);

C,

do.

in

pancreas

of frog

(after

Mathews).

dermal

fibrils

and basal

filaments,

your

archeoplasm

and

ergasto-

plasm,

and

probably

your

idiozomes,

plasmosomes,

and

many

other

histological

minutiae

f.

The

position

of

these

bodies

with

regard

to

the other

cell-

structures

is

carefully

described.

Sometimes

they he in the

neighbourhood

of

the nucleus

itself, that is

to say

in proximity

to

the

fluid

boundary

surface

which separates

the nucleus

from

the

*

Mitochondria

are

threads

which

move

slowly

through

the

protoplasm,

some-

times

break

in

two,

and

often

tend

to radiate

from the

centrosphere

or division-centre

of

the cell. The

nucleoli are two or

more

Opaque

bodies

within

the

nucleus,

which

keep

shifting their

position

;

within

the

cytoplasm many

small

fatty

bodies

likewise

move

about,

and

display

the

Brownian oscillation,

t

Cf. A. Gurwitsch, Morphologie

und Biologie

der

Zelle,

1904,

pp.

169-185;

Meves,

Die

Chondriosomen

als Trager

erblicher

Anlagen,

Arch.

f.

mikrosk.

Anat.

1908,

p.

72;

J.

0.

W,

Barratt,

Changes

in

chondriosomes,

etc.,

Q.J.

M.S.

LVin,

pp.

553-566,

1913,

etc.;

A. P.

Mathews,

Changes in

structure

of the pancreas

cell,

etc.,

Journ.

Mc/rph.

xv

(Suppl.),

pp.

171-222,

1899.


5/7

VIIl]

OF

RADIATE PATTERNS

619

among

our diatoms; but when it does so, it

is

looked

upon as

the

mark

and

characterisation

of

the

allied genus

Arachnoidiscus.

A

simple

case,

introductory

to others of

a

more

complex

kind,

is

that

of

the

radial canals

of the

Medusae. Here,

in

certain

cases

e.g.

Eleutheria ,

the

usual

arrangement

of

eight radial

canals is not

seldom

modified,

as

for

example,

when

two

or

more

of them

arise

14

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