DR. MARTIN BARRY'S RESEARCHES IN EMBRYOLOGY. 313 



The Ovisac of Amphibia and Fishes (" Chorion' of Authors) compared with the Ovisac 



of Mammalia. 



34. The ovisac of Amphibia, and that of Fishes, improperly called the " chorion," 

 first presents itself in a very similar condition to the ovisacs of Mammalia and Birds, 

 viz. size, the 50th of a Paris line-J- and less ; form, generally elliptical or ellipsoidal ; 

 contour, in plaits or folds. The chief difference consists in the fluid of the ovisac not 

 generally (though in some instances) presenting the peculiar granules (8.) described 

 as occurring in Mammalia and Birds. 



35. Plate VI. fig. 31 . Ovisacs of the Cod, vV" to ^"'. Contour in folds. Germinal 

 vesicle (c) in the centre, with its numerous germinal spots {h) \. 



36. Plate VI. fig. 27. Ovisac of the common Frog, ("chorion" of R. Wagner §, 

 from whom I take this figure,) vV'" = ^- germinal vesicle; b. germinal spots (many J); 

 e. membrana vitelli, yelk pellucid. 



37. Plate VI. fig. 32. Ovisacs of the Whiting, -f'" to -f'". There is a trace of yelk {d), 

 with something like the peculiar granules {§) of the ovisac in Mammalia and Birds 

 in the fluid of the ovisac. Compare with fig. 10. Plate V. from the Cat, and fig. 21. 

 Plate V. from the Pigeon. 



38. Plate VI. fig. 33. Ovisacs of the Haddock. Yelk {d) circumscribed by its 

 proper, and here very delicate membrane. 



39. Plate VI. fig. 27^. Ovisac || of the Coluber natrix: b. germinal spot (single;}:); 



c. germinal vesicle ; d. yelk ; e. membrana vitelli. 



40. Plate VI. fig. 28. Ovisacs of the common Frog, J'" : b. germinal spot ; c. ger- 

 minal vesicle ; e. membrana vitelli ; h. proper membrane of the ovisac ; d'. a spot which 

 I always find on the internal surface of the membrana vitelli of the Frog in ovisacs 

 of about this size. This spot does not appear to have been hitherto described. It 

 is generally elliptic, rarely round, has a well-defined contour, and is perhaps slightly 

 lenticular in form. In this instance it measured -^" in length, and is often of about 

 the same size. It appears to be composed of granules. 



41. Plate VI. fig. 34. Ovisac of the Turbot, tV'" * ^y membrana vitelli now visible; 



d. yelk, with oil-like globules (*) around the germinal vesicle. Compare with fig. 25. 

 Plate V. from the common Fowl, and fig. 16. Plate V. from the Hog. 



42. Plate VI. fig. 35. Ovisacs of the Salmon, tV'" to ^"', in nearly the same stage of 

 formation as the ovisac of the Turbot, fig. 34. At g are seen some of the peculiar 



f = 5-^ of an English inch. 



X Professor R. Wagnek finds a single spot in cartilaginous, and many spots in osseous Fishes. He finds also 

 a single spot in the scaled, and many spots in the naked Amphibia. 



§ Beitrage zur Geschichte der Zeugung und Entwickelung, tab. ii. fig. 6. a. (aus den Abhandlungen der 

 Mathematisch-physikalischen Klasse der Konigl. Bayer. Akad. der Wissenschaften in Miinchen besonders 

 abgedruckt). 



II " Chorion" of R, Wagnbr, from whom I borrow this figure. (Beitrage, &c., tab. ii. fig. 7 c.) 

 MDCCCXXXVIII. 2 S 



