102. M. Ussow’s Zoolugico-Embryological Investigations. 
judged from the greater or less maturity of the ova contained 
in them), and continuously (as quite young ova may always 
be found in them), and, indeed, as diverticula of the epithelial 
membrane of the ovary. The primitive ovicell, or the future 
so-called formative vitellus of the composite ovum, is nothing 
but a more developed cell of the epithelial coat of the ovary, 
which constantly growing cell, with the epithelium surrounding 
it, separates more and more from the ovarian spaces, and ~ 
finally remains united to the central mass of the ovary only 
by a longer or shorter peduncle. In the further development of 
the ovary the racemose or lobate form of that organ is due to 
the number of such Graafian follicles attached to peduncles 
and the number of young immature ova enclosed in them. 
The development of the ova always commences in the central 
part of the ovary, and increases pretty regularly towards its 
periphery, where the Graafian follicles and the ova (1-6 millims. 
in diameter) attain their full development. ~The relation to 
the ovary of the entrance into the unpaired (Sepia, Loligo, 
Sepiola, Rossia) or more rarely patred (Ommastrephes, Argo- 
nauta) oviduct (paired oviducts are always equally developed) 
is always the same in all the Cephalopoda investigated by me ; 
and the mode of escape of the mature ova first into the ventral 
cavity, and then their gradual passage into the oviducts, which 
contract peristaltically (Avgonauta*), and are sometimes re- 
peatedly twisted and bent, remind one of the similar processes 
im some Carnivora (Lutra). The naked ovicellt (gymnocyta), 
with the nucleus (= germinal vesicle) and the nucleolus 
(=germinal spot), grows simultaneously with the Graafian fol- 
licle, so that at first both increase in size pretty uniformly. But 
soon the growth of the Graafian follicle advances more rapidly 
by multiplication (longitudinal division) of the cells of the 
membrana granulosa, which forms, on the inner surface, a 
series of longitudinal and transverse folds penetrating into the 
vesiclet. The blood-vessels lying on the surface of the epi- 
thelial envelope penetrate into the interspaces of the above- 
mentioned folds, by which means both the considerably en- 
* The oviducts of this animal, taken out of the body and laid in water, 
continue to contract for a long time, by which means it becomes possible 
to obtain perfectly fresh ova belonging to different stages of segmentation. 
Ova procured in this manner, or even taken out of perfectly mature 
Graatian follicles, generally undergo further development. 
+ In Loligo and Argonauta at this time 0-008 millim. in diameter. 
t In Sepa these folds are double, but only the inner ones form the 
diverticula described below; the outer ones, on the contrary, form a 
uniformly diffused layer between the inner ones and the thin theca folli- 
culi. Between the two kinds of folds the blood-vessels ramify, and new 
ovicells originate. 
~ 
