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" Researches in Embryology T First Series. By Martin 

 Barry, M.D., F.R.S.E., Fellow of the Royal College 

 of Physicians in Edinburgh. 



This paper, lately read before the Royal Society, is divided into two 

 parts. In the first part the author describes the origin and structure of 

 the ovisac, a vesicle common to all vertcbrated animals, but hitherto re- 

 garded as the inner membrane of the " folliculus Graafianus" in Mammalia, 

 and by some authors denominated tlie " chorion" in other Vertebrata. 

 He also describes the real nature of the " folliculus Graafianus," and its 

 relation to the calyx of the Bird ; tlie germinal vesicle and its contents, 

 as being the most primitive portion of the ovum ', the order of formation 

 of the several other parts of the ovarian ovum ; and the true chorion of 

 Mammalia as being a structure superadded within the ovary. 



In the second part the author describes a granulous tunic of the ovum 

 of Mammalia not hitherto observed ; the manner of origin of the " mem- 

 brana granulosa" of authors ; the different situations of the ovum in the 

 Graafian vesicle at certain periods ante coitum, not hitherto observed ; 

 and certain structures by means of which the ovum is made to occupy 

 these several situations. 



The following are the principal facts made known by Dr Barry in this 

 memoir ; but other facts are also mentioned, which he intends to make 

 the subject of a future communication. In Mammalia and in Birds the 

 germinal vesicle and its contents are those parts of the ovum which are 

 first formed. The germinal vesicle at an early period is surrounded by 

 peculiar granules, forming an envelope not hitherto described. Tlie 

 ovum of all vertebrated animals is contained in a vesicle (the " chorion" 

 of some authors, as found in Birds, Amphibia, and Fishes), which is es- 

 sentially the same in structure wherever found, and which he thinks it 

 desirable universally to denominate an ovuac. This vesicle is the 

 '^ couche interne" of the Graafian vesicle, as described by Professor Baer. 

 The Graafian vesicle of Mammalia is nothing more than an ovisac that 

 has acquired a covering or tunic, susceptible of becoming highly vascu- 

 lar, which covering is the " couche externe" of the Graafian vesicle as 

 described by Baer. The ovisac of Birds, Amphibia, and Fishes, (*' cho- 

 rion" of some authors), acquires in like manner a covering or tunic, sus- 

 ceptible of becoming highly vascular ; and by the union of the ovisac with 

 this covering, there is constituted a structure analogous to the Graafian 



• Dr Martin Barry's previous obser\ation8 on Embryology having appeared 

 in this Journal, we judge it proper to put our readers in possession of the above 

 notice of his further discoveries in this important branch of Natural Historv. 

 Edit. 



