3^6 The Oogenesis of the Tortoise 



stant in eggs of the same size. It also retains its affinity for nuclear 

 stains. The number of nucleoli remains about the same, and they retain 

 their position at the periphery of the germinal vesicle. They still vary 

 in size, and do not seem to grow perceptibly after their formation, being 

 scarcely larger in the large egg, represented in Plate VII, Fig. 87, than 

 in eggs like those represented in Plates IV, V, VI. 



The nuclear reticulum remains visible as far as I have been able to 

 trace the germinal vesicle in later stages. After the stage represented 

 in Plate VII, Fig. 87, the egg becomes so filled with yolk that it is 

 difficult to section it successfully. 



The distance of the germinal vesicle from the cytocenter increases with 

 the growth of the egg, while its distance from the periphery remains 

 about the same, as is evident from an inspection of the plates. Compare, 

 for instance, Figs. 86 and 87 with Figs. 70, 71, 75. From the very 

 beginning, the germinal vesicle lies in the peripheral zone, between the 

 subcuticular layer and the cytoccel, and continues to occupy that position 

 even as late as those eggs represented in Plate VII, Figs. 84, 85, 86, 87. 

 In Plate II, Figs. 34, 35, 36, 38, 39 and 49, 50, 51, the outer limit of the 

 cytocenter, the cytoccel, is distinctly seen. Note that its relation to the 

 germinal vesicle is about the same in all these cases. It intersects the 

 germinal vesicle at its lower one-fourth. Comparing these figures with 

 the very young eggs of the first stage, as, for instance, Plate I, Figs. 12, 

 14, 16, 17, it Mali be seen how closely these relations are maintained 

 throughout the first and second stages. Comparing again these with the 

 eggs of considerable size of the third stage, represented in Plate VII, 

 Figs. 84, 85, 86, it will be seen that the germinal vesicle occupies the 

 same relative position with reference to the cytoccel. The one striking 

 difference between them is the increased distance between the cytocenter 

 and the germinal vesicle. This is especially evident in Plate VII, Fig. 87. 



The cytocenter is still visible in eggs as large as that represented in 

 Plate VII, Fig. 87, and in much larger eggs (Fig. 88) where the cyto- 

 plasm is crowded with the regular yolk-bodies. The form of the cyto- 

 center in these large eggs is variable. It is still very distinctly differen- 

 tiated by orange G. (Plate VII, Fig. 86) ; by acid fuchsin (Fig. 87) ; 

 and by hasmatoxylin (Plate VII, Fig. 88). In eggs like those of Plate 

 VII, Figs. 84, 85, the cytocenter still retains much of the typical char- 

 acters of the attraction sphere of younger eggs, it being as yet not invaded 

 by the yolk-bodies. But in eggs like those of Plate VII, Fig. 86, the 

 great increase of the yolk, both aroimd and within it, nearly obscures it. 

 The circular form is still maintained, and distinctly differentiated from 

 all else it is doubtless a remnant of the denser central portion seen in 



