102 M. Ussow'd Zoolo<jico-Emhrijolo(jicid In vest i(jat ions. 



judged from the greater or less maturity of the ova contained 

 m them), and continuoui^ly (as quite young ova may always 

 be found in tliem), and, indeed, as diverticula of the opitholial 

 membrane of the ovary. The primitive ovicell, or the future 

 so-called formative vitelfits of the composite ovum, is nothing 

 but a more developed cell of the epithelial coat of the ovary, 

 which constantly grooving cell, with the epithelium surroundi!)g 

 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 vnjmired {Sepia, Loligo, 

 Sepiola, Rossia) or more rarely j^aiVec? [Ommastrejdies, 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 tlieir gradual passage into the oviducts, which 

 conti'act peristaltically {^Irgonaufa*), and are sometimes re- 

 peatedly twisted and bent, remind one of the similar processes 

 in some Camivora (Lutra). The naked ovicellf {^ymnocyta) ^ 

 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 

 memhrana granulosa, which forms, on the inner surface, a 

 series of longitudinal and transverse folds penetrating into tlic 

 vesicle J. 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 cn- 



* The oviducts of this animal, taken out of the hody and laid in water, 

 continue to contract for a long time, by which means it becomes possible 

 to obtain perfectly fiesh ova belonging to different stages of segmentation. 

 Ova procured in this manner, or even taken out of perfectly mature 

 Graafian fullicles, generally imdergo fiu-ther development. 



t In Lolujo and Art/onatda at this time 00()8 millim. in diameter. 



\ In Sepia these folds are double, but only the inner cues form the 

 diverticula described below ; the outer ones, on the contrary, form a 

 uniformly diffused layer between tlie inner ones and the thin ihecn folli- 

 culi. Between the two kinds of folds the blood-vessels ramify, and new 

 pvicells originate. 



