Jolm P. ]\rnnson 347 



the relation of the yolk to the cytoccel and the relation of the latter to the 

 germinal vesicle. 



Fig. 87. Section of larj^e egs. showing the germinal vesicle at the peri- 

 phery, and the cytocenter, now an irregular mass of deeply staining granules. 

 The outer zone has become narrowed by the encroachment of the inner yolk 

 layer; the inner cytocoel still visible as a spongy zone of protoplasm. 



Fig. 88. Section of a large egg, showing the cytocenter surrounded by 

 fully developed yolk granules; the inner cytocoel, i. cy. c, now a narrow 

 zone of uniformily small yolk-bodies; the peripheral zone, p. z., now filled 

 with well developed yolk-bodies especially in the inner yolk layer, t. y. I.: 

 the outer cytocoel, o. cy. c, evident from the less perfectly developed yolk- 

 bodies resembling those of the inner cytocoel, i. cy. c; the outer yolk layer, 

 0. y. I., with well developed yolk-boc'ies: and the subcuticular layer, ,s'c. /. 



Fig. 89. Portion of the yolk of the largest eggs showing yolk formation 

 and oil globule. Killed in the usual way, but not imbedded. Mounted on the 

 slide and treated with iodine, showing oil globules unstained by iodine; 

 arrangement of yolk-bodies around these large unstained globules, and their 

 occasional breaking up into clusters of smaller globules often containing 

 a large one in the center. 



Fig. 90. Section of a cytocenter highly magnified, showing a small dark 

 central body, surrounded by indistinct zones of granules, the outer less dense, 

 and this again surrounded by a third outer zone apparently loosely reticulated 

 in the meshes of which there seems to be a system of astral rays proceeding 

 from the central mass. 



Fig. 91. Section of a germinal vesicle in the early stage of development 

 before true nucleoli have developed, and before the nuclear matrix has 

 become opaque by the formation of granules. 



Fig. 92. The ovary of the tortoise as seen with the naked eye, showing 

 the various stages of the developing eggs. The smallest eggs mark the posi- 

 tion of the germinal ridges lying between the larger eggs. 



Figs. 93, 94, 95. Oogonia showing increase in size previous to division to 

 form oocytes; stroma cells, with no follicle yet formed; nucleus in various 

 stages of growth; the attraction sphere; the relation of the latter to the 

 nucleus and to the outer protoplasmic zone of cytoplasm, the peripheral zone. 



Figs. 9G and 97. Young growing oocytes, showing in the young germinal 

 vesicle, bead-like chromatin network apparently imbedded in band of un- 

 stained linin substance; nucleoli forming in the interior, some of them 

 already vacuolated; typical spheres with indistinct centrosomes, but distinct 

 circles of microsomes with evidence of radial striations proceeding outward 

 from the center; the relation of the sphere (cytocenter) to the germinal 

 vesicle; the evident cytocoel, cy. c, Fig. 97, separating the cytocenter, c. c, 

 from the peripheral zone of cytoplasm, p. z. 



Fifi. 98. Yolk-bodies of various sizes stained in iodine and showing in 

 the larger a central Ijody .that is not so strongly affected by the stain and 

 appearing like vacuoles but evidently some differentiated solid substance. 



Fig. 99. Yolk-body composed of minute spherical granules throughout. 



Fig. 100. Yolk-sphere homogeneous throughout. 



Fig. 101. Smaller yolk-body filled with smaller yolk spheres but larger 

 than those of Fig. 99. 



