OVARIES IN TELEOSTEAN AND ELASMOBRANCH FISHES. 21] 



Fig. 10. — Zoarces, Section of more advanced egg with "yolk-nucleus" 

 breaking up into fragments, the more internal of which are " dissolving." 

 Hsemalum. Zeiss. A, ocular 4. 



Tig. 11. — Zoarces. Section of ovum with yolk-nucieus cut tangentially 

 to show reticular structure of the same. Hsemalum. Zeiss A, ocular 4. 



Fig. 12. — Zoarces. 15*5 cm. Sept. 18. Section of more advanced 

 ovum. The "yolk-nucleus " has broken up into fragments, and the latter are 

 " dissolving." Amongst the fragments of the yolk-nucleus are clusters of 

 very minute oil drops (not well shown in the figure). The centrosphere (?) 

 in upper left-hand corner has enlarged, and is degenerating. Hermann's fluid 

 and tliiouin. Zeiss A, ocular 4. 



Fig. 13. — Zoarces. 132 cm. Feb. 24. Young developing ovum slightly 

 more advanced than that shown in Fig. 6, Yolk-nucleus has severed its con- 

 nection with the germinal vesicle, but is still hemispherical. Vacuoles in the 

 yolk-nucleus are shown. Borax carmine, X 400. 



Figs. 14, 15. — Zoarces. 80 cm. From section of the ovary. Karyoki- 

 netic division of oogonia. Hsemalum. Zeiss D, ocular 4. 



Fig. 16. — Zoarces. Section of small ovum, showing turgid condition of 

 the cells of the follicular epithelium over greater part of the surface, indi- 

 cating commencing degeneration of the egg. Carmalum. Zeiss A, ocular 4. 



Fig. 17. — Zoarces. Section at the surface of an immature ovum, "5 mm. 

 in diameter, showing membrana propria foUiculi, follicular epithelium, zona 

 radiata, and (next the vitellus) the zonoid layer. Hsemalum. X 400. 



Fig. is. — Zoarces. Section at the surface of a nearly ripe egg, 2"5 mm. 

 Here the zona radiata is much thicker, and the zonoid layer has disappeared. 

 Hsemalum. x 400. 



Fig. 19. — Spinax niger. Section at the surface of an immature ovum, 

 1'5 mm. in diameter. The follicular epithelium has withdrawn from the egg 

 membrane, and its cells are seen to be provided with fine processes which 

 enter into the membrane. Borax carmine, x 400. 



Fig. 20. — Zoarces. 13"2 cm. Feb. 24. Section of an abortive follicle. 

 The follicular epithelium has proliferated, and is filling up the cavity originally 

 occujiied by an egg, remains of which are still present (ei.). At one place (f/r.) 

 the follicular epithelium still retains its epithelial character, and is only one or 

 two cells deep. In the same region fragments of the zona radiata remain. 

 In the dead protoplasm of the egg and in the follicular epithelium may be seen 

 vacuoles, representing the fatty products of degeneration of the egg, and oil 

 droplets. Borax carmine. Zeiss A, ocular 4. 



PLATE 16. 



Fig. 21. — Zoarces. 13'2 cm. Feb. 24. Portion of a transverse section 

 of the ovary. The egg cavity of the large ovigerous pouch in the middle of 

 the figure is entirely filled up with ihe tissue formed from the follicular epi- 



