Early Development of the Ilen^s Egg. Ill 



twice, and produced a "nest" of four nuclei (Fig. G, sn). It is 

 difficult to determine whether or not such nuclei later migrate from 

 the nests to the margin of the primary area and there participate in 

 the production of the accessory cleavage. The writer believes not, 

 because nests containing many small fragments of nuclei are found 

 in slightly later stages, and such nests are located in the same posi- 

 tion as the earlier ones. This would seem to indicate that the 

 nuclei, after sinking down into the coarse granules, continue to 

 divide and fragment, finally disappearing altogether. If this be 

 true, then we see the beginning of the degenerative ag(mcy which 

 will cause all of the supernumerary nuclei to disappear. 



An egg showing a case of fragmenting nuclei is outlined in Fig. 

 10. It is a three-celled stage, and the degenerating nucleus is close 

 to the margin of the primary area. All of the sperm nuclei, except- 

 ing one, are located much more peripherally than in the preceding 

 egg (cf., Figs. 9 and 10). The difference in position of the two 

 sets indicates the distance traversed by the nuclei during the time 

 intervening between the two stages. 



A section of the egg figured above gives one a good idea of the 

 character of the blastodisc in the early stage (Fig. 11). It also 

 demonstrates the point made above, that very often the first cleavage 

 membranes are not accompanied by a cleavage furrow. 



This egg furnishes still other points of interest, for in fixing it, 

 not all of the albumin was removed, and the thin chalazipherous 

 layer adheres to the vitelline membrane. Embedded in this layer 

 and next to the membrane are about ninety sperm heads, none of 

 which is located peripherally to the terminal ends of the cleavage 

 membranes (Fig. 8). 



The presence of the sperm heads in such large numbers, together 

 with their position at the central part of the disc, is important. It 

 can not be said that the scarcity of sperm nuclei in the disc (as 

 compared with the number found in the pigeon egg) is to be ac- 

 counted for by the "lack of sperms in the oviduct. Their location in 

 the central part of the disc only, shows that they must be attracted 

 there by a force which is strongest at the central point, and which 

 gradually diminishes toward the periphery. The attraction between 

 the protoplasm of the disc and that of the sperms is evidently neu- 



