490 General Notes. [May 
travel thence to the ovum; food-granules also appear in the 
outon of the germinal vesicle, and travel away from it; 
e the horseshoe-shape of the elk-mass as seen in section. 
se “The t time during which food-granules are thus passing from 
the follicular cells to the ovum may be called ‘the yelk-forming 
perio 
4 tr is succeeded by a period during which the vitelline mem- 
brane again becomes thin, the follicular cells are reduced to a 
single layer, and the cells are very thin and flat. This period 
may be called ‘the absorption-of-fluid pra since during it 
the ovum absorbs large quantities of fluid through the thin 
vitelline membrane and single layer of thin follicular cells, and 
thereby i increases largely in size. 
is is in turn succeeded by a third period, during which the 
follicular cells again become active, multiply, increase greatly in 
size, and give rise, between themselves and the vitelline mem- 
brane, toa deeply-staining homogeneous layer, which I will call 
the chorion. This period may be called ‘the chorion- -forming 
period. All these these periods are gone through while the 
ovum is still in the follicle. 
“Upon the bursting of the follicle and the reception of the 
ovum in the Fallopian tube, a few of the follicular cells remain 
attached to the chorion; the majority are left behind within the 
burst follicle. 
“During the passage along the Fallopian tube the vitelline 
enbi again increases in thickness, and the chorion, also 
increasing in thickness, absorbs fluid and becomes że albumen 
layer. Outside this now appears a new structure, zie shell or 
shell-membrane, of tough, parchment-like consistency,’ not 
staining with reagents. I have not yet traced the deposition 
of the shell to the activity of any special glands; but I can say 
that the shell-membrane does not increase at the expense of the 
chorion or albumen layer. 
“ After reaching the uterus both vitelline membrane and shell- 
membrane increase in thickness, but the albumen diminishes and 
di serving, ap arently, for the nutrition of the ovum. 
Immediately beneath the vitelline membrane a new layer is now 
seen in hardened preparations; but it may be shown that this 
layer is aed fluid, yielding a coagulum which stains deeply 
ents, the fluid being apparently derived, through the 
initia, from the uterine glands, 
“Tn Marsupialia = history of the vitelline membrane, save 
that ‘the egg ing period’ is not marked off from the ‘ab- 
sorption-of-fluid’ period, is similar to that in Monotremata. I 
have not been able to trace the beginning of the ‘chorion’ while 
the ovum is still in in the ovary in Marsupialia; but in an ovum of 
ž «Tn the laid of Echidna I have not detected calcic but 
s gives rie rise to gas when A win te ai salts, but that of Orni- 
