498 



STANLEY C. BALL 



less dark granules in the egg cytoplasm. It is plainly seen, 

 however, in the earher stages illustrated in text figures 4 and 9. 

 I can furnish no evidence concerning the union of the pro- 

 nuclei; the most careful search failed to disclose any trace of 

 centrosome and aster associated with the male pronucleus. 



4. Cleavage 



In the study of early cleavage in hving capsules a serious dif- 

 ficulty has been encountered in the thick bed of yolk which 



fni'cl 



Text fig. 12 Outline from life of a young embryo observed in the antrum of 

 the mother, cap., capsular membrane; mad, first macromere; mid, first 

 micromere; mit., mitochondrial mass; p.b., polar bodies. X 730. 



surrounds the embryos. Text figure 12 was drawn from an egg, 

 which, contrary to custom, had entered the antrum, become 

 surrounded by the capsular membrane, and, since no yolk cells 

 were enclosed, was conveniently easy to observe. If an attempt 

 be made to remove the embryos at this stage they fragment. 

 Late blastulae may be thus removed with some success (fig. 15). 

 The only alternative was a trial of various stains. As yet 

 I have not had much' success in staining the embryonic cells 

 and at the same time leaving the yolk sufficiently transparent. 

 Neutral red and methyl green were used to stain in vivo. Even 



