John P. Munson 329 



has not yet flowed out of it. The light areas might suggest, perhaps, 

 that it is not a mere reservoir or a single channel into which the liquid 

 substance is poured, which is also suggested by Plate IV, Pigs. 69, 70. 

 Its connection, real or apparent, with the germinal vesicle would be 

 strong evidence in favor of the theory of nuclear origin were it not for 

 the marked difference in staining between it and the contents of the 

 germinal vesicle. 



I have reasons for believing that it is not fatty in nature. The usual 

 method of imbedding and mounting emulsifies the oil globules which 

 arise in the egg during the formation of the true yolk-bodies, and causes 

 them to disappear entirely in the prepared material, whilst, as I shall 

 show presently, they are very large and numerous in material not so 

 treated. 



The stains which bring this yolk-nucleus most prominently into view 

 are acid fuchsin, saffranin and eosin. With these stains it is more con- 

 spicuous than any other part of the egg. It often resembles archoplasm 

 very closely. Its granular characteristics are most marked when stained 

 with acid fuchsin and saffranin. 



I have no reason to believe that this yolk-nucleus is at all permanent 

 or that it simply accumulates in the cytoplasm as the egg grows. It may, 

 apparently, be present or absent in eggs of equal size. Thus, compare, 

 for instance, the serial sections a, b, c, d, e, Plate III, Figs. 57-61, with 

 Plate III, Fig. 62, an egg of about the same size. The cytocenter is 

 present in both, but not the yolk-nucleus. 



The ijolh first makes its appearance as definite spherical yolk-bodies 

 when the egg has attained the size represented in Plates IV, V, VI. It is 

 certainly very suggestive that the yolk-nucleus is so very prominent 

 just before the yolk-bodies begin to form (Plate Y, Figs. 76, 77; Plate 

 VI, Figs. 78, 79, 80). Yet the yolk-nucleus is by no means peculiar to 

 this stage of growth, as it occurs just as frequently in the very smallest 

 eggs of the second period of growth (Plate I, Fig. 23; Plate II, Figs. 

 30, 31, 33, etc.). 



The yolk-hodies appear as small, bead-like bodies in little vacuoles, 

 one in each, arising between the subcuticular layer and the peripheral 

 zone of the cytoplasm (Plate V, Figs. 72-74, and Plate VI, Figs. 78, 79, 

 80). At first they are few, with long intervals between them (Plate V, 

 Figs. 72-74). Later they increase, both in size and in number (Plate 

 V, Figs. 76 and 77). 



They next arise in the cytoccel, forming a ring around the cytocenter 

 which has now increased greatly in size (Plate VII, Fig. 84). This 

 zone of yolk-bodies gradually broadens, encroaching, on the one hand, 



