60 ROBERT SCHARFF. 



ovum of osseous fishes is undergoing during its growth. In 

 the ripe gurnard's egg a large oil-globule is to be found at the 

 periphery of the yoke, and similar ones occur in many other 

 marine Teleosteans. The largest yoke spherules in the gurnard 

 (fig. 10) have a diameter of 0*015 mm. In the frog-fish 

 (Lophius piscatorius), however, their size varies from 

 0-018 up to 0-090 mm. (fig. 11). The contents in the latter 

 case consist, besides the small granules, of peculiar crescent- 

 shaped bodies and vacuoles. In many of them dark crystal- 

 line bodies were seen enclosed in a vesicle. Ovsiannikov 1 

 likewise makes mention of crystals and peculiar oval bodies as 

 occurring in the yolk spherules of Osmerus eperlanus. 



With regard to the process of budding from the nucleus 

 which I just described as leading to the origin of the yolk- 

 spherules, similar changes of the nucleus have been noticed by 

 various observers; but only Will 2 derives the yolk-spherules 

 from these buds. He investigated the intra-ovarian egg of 

 Amphibia. No other writer seems to have seen anything 

 corresponding to this process in Vertebrates. Roule, 3 Fol, 4 and 

 Balbiani 5 also describe the formation of diverticula from the 

 surface of the nucleus. The first two studied the ova of Asci- 

 dians, the latter those of Myriapods. However, the ultimate 

 fate of these diverticula containing nucleolar portions is to 

 become cells of the follicular epithelium, which in Teleostean 

 ova has been formed before those changes began. That the 

 yolk-spherules originate within the egg has been rigorously 

 maintained by some of the greatest authorities, such as Balfour 

 and Gegenbaur, but neither of the two mentions the budding 



1 Ovsiannikov, "Studien uber d. Ei hauptsachlich d. Knochenfische," 

 1 Mem. Acad. Imp. St. Petersb.,' vol. xxxiii, 1886. 



2 Will, " Ueber d. Entstehung d. Dotters und d. Epitbelzellen bei Ampin- 

 bien und Insekten," ' Zoologischer Anzeiger,' 1884. 



3 Roule, " La structure de l'ovaire et la formation des ceufs chez les Phal- 

 lusiadees," ' Comptes Rendus,' 1883. 



4 Fol, " Sur l'origine des cellules du follicule chez les Ascidiens," ' Comptes 

 Rendus,' 1883. 



5 Balbiani, " Sur l'origine des cellules du follicule chez les Geophiles," 

 ' Zoologischer Anzeiger,' 1883. 



