336 



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 diflPerent animals: — 1. 

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

 the Graafian follicle, and termed the ovisac, does not remain pei^ma- 

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

 Bird, the ovum, when escaping from the ovar}^ 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 chalazse 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. 



The Society then adjourned over the Vacation to Thursday, 

 November 17, 1853. 



