294 C. M. CHILD. 



nuclei have separated, \\hile on die other side it is still very 

 delicate and the nuclei an- Mill closely connected. The dense 

 mass in the upper p.irt <>t" the figure is the cytoplasm of a large 

 blastomere which has not yei .undergone the change in appear- 

 ance; its nucleus is in another section. 



Fig. 13 shows a section without any cell boundaries and with 

 \aciiolated cytoplasm in which one small nucleus is apparently 

 dividing. 



In Fig. 14 a constricted nucleus is shown. The cytoplasm 

 of a large dense blastomere is also seen in the figure. 



Fig. 15 shows another case which is to me very convincing. 

 The double nucleus is in a mass of cytoplasm which is denser 

 than the rest and still rather distinctly marked off from it. 

 Evidently this represents a blastomere. Here, as in Fig. 12, 

 the division of the nucleus apparently began from one side, for 

 the membrane is much more distinct on the side where separation 

 is most advanced and becomes more and more delicate toward tin- 

 other side. 



Fig. 1 6 represents a case of almost diagrammatic clearness in 

 which a large nucleus is apparently dividing from one side. 

 Other nuclei are in other sections of the egg. 



Figures of this sort might be multiplied indefinitely from 

 Richanls's material as \\ell as from my own. There is, I think, 

 but little chance of observational error here, for the nuclei are 

 relatively large and not crowded and in many cases almost 

 diagrammatically distinct. If pictures of this sort are of any 

 \alue as a criterion of the occurrence of amitosis, then the 

 e\ idence is certainly very strong for these cleavage stages. 



( )ne question, ho\u-\er. must be raised here, vi/., whether 

 these are normal stages in development or degenerating embryos. 

 To settle this point absolutely tin- study of later stagi-s i- neces- 

 sary and thus far 1 have not been fortunate enough to obtain 

 such si.iges. But in many proglottids practically every embryo 

 shows this syncytial condition and if this indicates degeneration, 

 then all, or almost all. the embryos of those proglottids are 

 degenerating. Ii seems probable therefore that \\e ha\e to do 

 here with normal stages in ihe development. 



