336 DR. MARTIN BARRY'S RESEARCHES IN EMBRYOLOGY^ 



PLATE VI. 



Fig. 27. Frog (from R. Wagner), h. Ovisac, -^", ("chorion" of Wagner (34.)); 



b. germinal spots, inanym the naA:e</ Amphibia (R. Wagner) ; c. germinal 

 vesicle ; e. membrana vitelli ; d. yelk, pellucid at this period. 



Fig. 274- Coluber Natrix (from R. Wagner), h. Germinal spot, single in the 

 squamous Amphibia (R. Wagner) ; c. germinal vesicle ; d. yelk, in its 

 membrane; h. ovisac ("chorion" of Wagner (34.)). 



Fig. 28. Frog {Rana temporaria, Linn.). A spot (d'), generally elliptical, and in 

 this instance vV" in length, which I always find on the internal surface 

 of the membrana vitelli of the Frog in ovisacs of about this size {-U") 

 (40.). b. Germinal spots ; c. germinal vesicle ; d. yelk ; e. membrana 

 vitelli ; h. ovisac. 100 diam. 



Fig. 29. Ditto. The membrana vitelli (e) rendered visible by maceration -J-, c. The 

 germinal vesicle, indistinctly seen in the centre of (d) the yelk ; e. mem- 

 brana vitelli ; h. ovisac. 60 diam. 



Fig. 30. Salmon (Salmo Salar, Linn.). A very early stage in the formation of the 

 ovum, nearly corresponding to figs. 18. and 19. Plate V. from the Bird, 

 and to figs. 1. 2. and 3. Plate V. from Mammals (17-)- ^'- Germinal vesi- 

 cles, the largest ^^th of a Paris line in diameter ; their contents consist- 

 ing chiefly of minute oil-like globules of a yellowish colour. Compare 

 these vesicles with the germinal vesicles in fig. 35. from the same fish. 

 One of the germinal vesicles in fig. 30. has another vesicle external to it. 

 Is this a minute ovisac just formed? (See the manner of origin of the 

 ovisac (23.)). 240 diam. 



Fig. 31. Cod {Gadus Morrhuaj Linn.). Ovisacs, ■^"' to^'" ; the contour in folds 

 (34.). The yelk is not yet visible, being pellucid at this period, b. Ger- 

 minal spots, mani/ in osseous Fishes (R. Wagner) ; c. germinal vesicle, 

 its fluid tinged with yellow; *. oil-like globules; h. ovisac. 100 diam. 



Fig. 32. Whiting {Gadus Merlangus, Linn.). Ovisacs V" to i'"; the contour in 

 folds (34.). c. Germinal vesicle ; g. peculiar granules in the fluid of the 

 ovisac (8.); h. proper membrane of the ovisac; d. incipient yelk (24.). 

 100 diam. 



Fig. 33. Haddock {Gadus JEglefinus). The yelk {d) now visible as well as its 

 proper membrane (e). 6. Germinal spots ; c. germinal vesicle ; /^.proper 

 membrane of the ovisac. 100 diam. 



Fig. 34. Turbot {Pleuronectes maximus, Linn.). Membrana vitelli {e) now visible. 



c. Germinal vesicle ; h. ovisac ; d. the yelk, consisting of oil-like globules 

 immediately around the germinal vesicle, and of granules on the internal 



t As recommended by R. Wagneb. 



