314 DR. MARTIN BARRY'S RESEARCHES IN EMBRYOLOGY. 



granules (8.) in the fluid of the ovisac. Compare with fig. 16. Plate V. from the 

 Hog, and fig. 25. Plate V, from the common Fowl. 



43. Plate VI. fig. 29. Ovisac of the common Frog; the yelk (</) becoming opake, 

 and the germinal vesicle (c) in its centre. 



44. Plate VI. fig. 36. Ovisac of the Salmon, acquiring a proper covering or tunic. 

 In this instance two minute ovisacs are included (57.) by that portion of the covering 

 which enters into the formation of the pedicle. 



45. Plate VI. fig. 37. Ovisacs of the Salmon, no longer to be distinguished from 

 their pfoper coverings or tunics, with which they have coalesced to form vesicles (cap- 

 sules) analogous to the Graafian vesicle of Mammals. The vesicles have been crushed, 

 and the yelk is seen escaping by the pedicles, taking with it its proper membrane (e). 

 See the ideal section, Plate VI. fig. 38^ ; which shows why the yelk escapes by this 

 passage. 



46. Plate VI. fig. 38. Perfect calyx of the Salmon, with its pedicle. 



The Graafian Vesicle of Mammals, how related to the Calyx of Bii^ds, Amphibia, and 



Fishes. 



47. Should the accuracy of the figures now compared be confirmed by future ob- 

 servation, it may perhaps be considered as established, in the first place, that the pri- 

 mitive elements of the ovum of Birds, Amphibia, and Fishes, are contained in a vesicle 

 (the "chorion" of authors) essentially the same as that which I have called thQ ovisac 

 of the Mammalia ; secondly, that if it be, as I suppose, by acquiring a proper covering 

 or tunic-)- that the ovisac of the Mammalia becomes what has been by others called a 

 Graafian vesicle, the ovisac of Birds, &c. by acquiring a proper covering or tunic -f- 

 presents a structure (capsule) analogous thereto ; and thirdly, that it is the structure 

 so constituted in the Bird, &c., which on becoming pendent from the ovary, and in- 

 vested by what there is of tTie substance of the ovary, as well as in some instances by 

 the peritoneum :j:, has been called a calyx §. 



48. From the foregoing it appears that the Graafian vesicle is not, as it has been 

 supposed to be, a structure peculiar to Mammalia. Nor is it correct to consider the 

 Graafian vesicle of Mammalia as analogous to the whole calyx of other animals. It 

 corresponds to no more than the two internal membranes, viz. the ovisac and its 

 proper vascular covering, the remainder of the calyx being derived from the ovary, with, 

 in Birds, some Amphibia and some Fishes, a peritoneal covering; and however incon- 



t Susceptible, as already said, of becoming highly vascular. 



X In other instances the peritoneal investment does not enter into the formation of the calyx. We find ex- 

 amples in the naked Amphibia, in Ophidian and Saurian Reptiles, and in most osseous Fishes, where the ovaries 

 are sacs, having the calyces pendent in their interior. 



§ My researches have not yet been extended to the Invertebrata ; but I am by no means disposed to con- 

 sider the existence of the vesicle, which I have called the ovisac, as limited to vertebrated animals. 



