330 The Oogenesis of the Tortoise 



on the perijiheral cytoplasmic zone and, on the other hand, on the cyto- 

 center. The yolk-bodies then form rapidly inward toward the central 

 portion of the cytocenter, developing even in the central portion of it 

 (Plate VII, Fig. 86). The yolk-bodies first formed in the cytocoel are the 

 largest; and those latest formed in the cytocenter are the smallest at this 

 stage. The yolk-bodies first formed at the subcuticular layer, although 

 the oldest, do not grow so rapidly. They seem to stain differently from 

 the larger spheres nearer the center of the egg (Plate VII, Pig. 86). In 

 a very much larger egg, the cytocenter can still be seen, having now the 

 appearance of a mass of granules (Plate VII, Fig. 87). At some dis- 

 tance from this, there is a zone forming a ring around the center in 

 which the yolk-spheres are still very small and showing the original 

 reticular cytoplasm filled with small yolk-bodies. Notice the light ring 

 surrounding the cytocenter in Plate VII, Pig. 85. The same feature is 

 visible in a very much larger egg, when the yolk-bodies have become very 

 large and nearly uniform (Plate VII, Fig. 88, i. cy. c). It is now a 

 narrow ring, encircling the cytocenter about half way between the latter 

 and the periphery of the egg, and consisting of closely-packed yolk-bodies 

 of minute size and having considerably less affinity for the stain. Both 

 in this stage and in the preceding the yolk-bodies first formed at the 

 periphery have become quite large; smaller spheres have developed out- 

 ward, so as to encroach on the subcuticular zone, and likewise inward. 

 Yet the yolk-ring first formed has not been merged into that of the sec- 

 ond, but is separated from it by a zone of minute yolk-spheres similar to 

 those of the inner ring. 



Comparing the yolk of these eggs with the yolk of eggs merely killed 

 with the same preserving fluid, and preserved in 70 per cent alcohol, I 

 found that there are certain bodies in the latter yolk which are not to be 

 seen in the mounted section (Plate VII, Fig. 89). These bodies vary 

 in size, but some of them are large enough to be seen with the naked eye. 

 They are yellow to the naked eye. Under the microscope they appear 

 white or transparent almost like water. They become especially promi- 

 nent when iodine is applied to the preparation. This solution stains all 

 the true yolk-bodies a deep yellow, but has no effect on the spheres under 

 consideration. The yellow yolk-bodies, especially the smaller ones, seem 

 to cling to the much larger white spheres so as to form clusters with the 

 white spheres in the center. Smaller spheres or vacuoles can sometimes 

 be seen inside the larger ones. Instead of a larger white sphere, there 

 may be a bunch of very little ones having the same optical properties. 



The application of chloroform has a peculiar effect on such a prepara- 

 tion. As soon as the chloroform is applied, the white globules, wherever 



