John P. Munson 337 



Plate VII, Fig. 85. So far as my observations extend on these larger 

 eggs, the cytocenter exists wherever the germinal vesicle exists. 



The yolk-nucleus is prominent in these eggs. It is especially con- 

 spicuous in eggs at the transition between the second and the third stage 

 of growth (Plate IV, Figs. 68, 71; Plate V, Figs. 72, 73, 74; Plate VI, 

 Fig. 78, 79, 80, 81, 82). It is, however, not confined to this transition 

 period, but it is found in eggs of all stages of the second period of 

 growth (Plate I, Figs. 23, 26; Plate II, Figs. 30, 33, 36, 37, 38, 39, 42, 

 44, 51 ; Plate III, Figs. 53, 54, 57, 58, 59, GO, 61, 63, 64) . The principal 

 characteristics of the second period of growth, besides the appearance 

 of the nucleoli in the germinal vesicle, has previously been stated to be 

 the granular condition of the cytoplasm; that of the third stage, the 

 origin of the true yolk-bodies. 



The yolk-nucleus has no such constant morphological feature as the 

 germinal vesicle and centrosome or cytocenter. There is no apparent 

 limit to the number that may exist in an egg (Plate III, Fig. 59; Plate 

 IV, Fig. 69). The size varies greatly even in different sections of the 

 same egg (Plate VI, Fig. 80). They are often circular in section and 

 regular in outline (Plate III, Fig. 54; Plate II, Fig. 37), or they may 

 be oval (Plate IV, Fig. 66) ; or they may be greatly elongated (Plate IV, 

 Fig. 68) ; or they may be twisted (Plate II, Fig. 31; Plate IV, Fig. 70) ; 

 or they may be very irregular (Plate IV, Fig. 71; Plate VI, Figs. 80, 

 83). In the smaller eggs, they are often located near the periphery 

 (Plate II, Figs. 33, 36, 42; Plate III, Fig. 63; Plate IV, Fig. 68). I 

 assume that these are the bodies that were seen by Clark, 20. They are 

 also found in the neighborhood of the cytocenter (Plate I, Fig. 23; 

 Plate II, Figs. 37, 38, 51; Plate III, Fig. 54). But their greatest 

 development seems to occur in the neighborhood of the germinal vesicle 

 (Plate III, Figs. 57, 58, 59; Plate IV, Figs. 69, 70), and may partly 

 surround the germinal vesicle (Plate VI, Fig. 79). It is often so close 

 to the germinal vesicle as to make the hypothesis of continuity with the 

 granular nucleoplasm extremely suggestive (Plate II, Figs. 37, 47, and 

 Plate IV, Fig. 69, 70, and Plate VI, Fig. 79, 83). I can discover no law 

 regarding its distribution throughout the egg, except that it usually 

 occurs in that region of the cytoplasm which I have designated the 

 cytocoel (Plate II, Fig. 31, 38, 51; Plate III, Fig. 57, 58, 59, 60, 61; 

 Plate IV, Figs. 67, 69, 71; Plate V, Figs. 72, 75, 77; Plate VI, Figs. 

 78, 80, 81, 82, 83). 



There are good reasons for believing that this yolk-nucleus is more or 

 less fluid, and that it spreads throughout the cytoplasm sometimes by 

 ordinary diffusion; but, at other times, by actual currents. These cur- 



