342 The Oogenesis of the Tortoise 



germinal vesicle, a clear area around the centrosome, and an accumulation of 

 granules in the nucleus, probably the beginning of a nucleolus. 

 " Fig. 17. Oocyte more highly magnified, showing the nuclear reticulum, 

 the bead-like chromatin bodies of various sizes, and in the cytoplasm a cen- 

 trosome with its two rings of microsomes and their relation to the germinal 

 vesicle. 



Fi(i. 18. A more advanced oocyte with the first undoubted nucleoli in the 

 germinal vesicle, and the cytoplasm filled with granules that obscure the 

 microsome rings of the sphere. 



Fid. 19. A still more advanced egg with a conspicuous sphere. 



Fi(!. 20. Growing egg with a more or less fibrous archoplasmic sphere. 



Fig. 21. Egg with large, almost homogeneous cytocenter, probably due to 

 the kind of stain (hematoxylin) used. 



Fig. 22. Egg showing a typical sphere consisting of a central body, centro- 

 some, a clear zone surrounded by a circle of microsomes, which again is 

 surrounded by a zone of radial fillers extending to the cytoccel, or outer circle 

 of microsomes. 



Fig. 2.3. Growing egg with true peripheral nucleoli in the germinal vesicle, 

 and in the cytoplasm a cytocenter with astral radiations and two oval yolk- 

 nuclei in its immediate vicinity. 



Fig. 24. Egg with a rather large, homogeneous centrosome, surrounded by 

 a zone archoplasm. 



Fig. 25. Egg with a very large, apparently homogeneous protoplasmic 

 cytocenter with a clear ring around it, and bearing a definite relation to the 

 germinal vesicle. 



P^'iG. 2G. Egg with a distinct centrosome, cytocenter with astral radiations 

 surrounding it; also in the cytoplasm a yolk-nucleus. 



PLATE II. 



Fig. 27. Egg with a large homogeneous cytocenter having very much the 

 appearance of archoplasm. 



Fig. 28. Egg with an indistinct circle of microsomes and astral radiations 

 packed into a bundle on one side giving the cytocenter an elongated appear- 

 ance, and extending nearly to the periphery of the egg. 



Fig. 29. Egg showing the open cytocoel, the outer limit of the cytocenter, 

 and its relation to the germinal vesicle. The peripheral zone of cytoplasm 

 extending from this cytoccel to the periphery, is here clearly seen. 



Fig. 30. Section of an egg showing a cytocenter in form of an aster with 

 a large yolk-nucleus on one side. The multiplication of nucleoli and their 

 variation in size is here evident. 



Fig. 31. A somewhat larger egg with an elongated body, probably a com- 

 bination of the archoplasm of the cytocenter with yolk-nuclei. 



Fig. 32. Section of egg showing a simple spherical cytocenter, possibly a 

 yolk-nucleus. 



Fig. 33. Section of egg at right angles to the egg axis, showing cytocenter 

 with astral radiations, and peripheral yolk-nuclei. 



Fig. 34. Section of an egg showing cytocenter with two circles besides the 

 inner one, and the relation of the outer circle, cytoccel, to the germinal 

 vesicle; a slight indication of asti-al rays. 



