306 Royal Society, 



of other animals. He more particularly adverts to a recently pub- 

 lished memoir by Dr. Keber, in which that physiologist describes 

 the penetration of the spermatozoon into the interior of the ovum, in 

 Unto and Anodonta, through an aperture formed by dehiscence of 

 its coats, analogous to the micropyle in plants. 



Small pellucid vesicles, lined with ciliated epithelium and enclo- 

 sing a revolving mulberry-like object, such as the author discovered 

 imbedded under the mucous membrane of the rabbit's uterus and 

 described in the Philosophical Transactions for 1839, have been like- 

 wise observed by Keber, not only under the mucous membrane, but 

 also and most frequently in some part of the canity of the abdo- 

 men. Keber considers these bodies to be fecundated ova. The 

 author agrees with Keber in considering them to be ova, but he does 

 not suppose them to be fecundated, nor does he think that their 

 membrane is the vitellary membrane ("zona pellucida"), which he 

 believes to have been absorbed. He considers such ova to have been 

 detached from the ovary along with their containing ovisac, which 

 in their new situation constitutes the ciliated capsule, and as they 

 present themselves in unimpregnated animals, he now believes that 

 the formation of a mulberry-like group of cells from the germinal 

 spot and the process of division and subdivision of the latter take 

 place without fecundation ; but when this happens, the mulberry is 

 not found to contain one cell larger than the rest, the nucleus of 

 which, according to his observations, is the embryo. He is further 

 of opinion, that in all cases of separation of ova, the ovisac or in- 

 ternal coat of the Graafian follicle is detached from the ovary, either 

 entire and along with the ovum, as in the instances alluded to, or 

 after the ovum has first escaped by rupture, as in the instance of the 

 fecundated ovum. 



The author is led to the following conclusions with reference to 

 the structures connected with the ovum in different animals: — 1. 

 That in the mammalia the vesicle he described as the foundation of 

 the Graafian follicle, and termed the ovisac, does not remain perma- 

 nently in the ovary, but is expelled and absorbed. 2. That in the 

 Bird, the ovum, when escaping from the ovary, is accompanied by 

 the corresponding vesicle — the ovisac ; and that the ovisac becomes 

 the shell-membrane of the Bird's egg. 3. That the expelled and lost 

 ovisac in the mammalia therefore corresponds to the shell- membrane 

 in the Bird. 4. That after the formation of the ovum the albumi- 

 nous contents of the ovisac in the mammalia correspond to the 

 albumen in the Bird's egg. 5. That the author's retinacula in the 

 mammalia, after all, find their analogue in the chalazae of the Bird ; 

 and that both have their origin in the granular contents of the ovi- 

 sac, which at an early period are in appearance just the same in 

 both. 6. That the shell-membrane of the Bird is thus a primary 



celL 



He then points out the position which from his observations is to 



be assigned to the several parts of the ovum in the language of 



" cells ; " and shows the presence of a plurality of ova in a Graafian 



follicle to be referable to the same cause as that producing more 



than one yelk (ovum) in the Bird's egg. 







