DEVELOPMENT OF THE EGG OF CLAVA LEFTOSTYLA. 



227 



nuclei. In Eudendrium and in the species of Tubularia referred 

 to above, it has been shown that in a considerable number of 

 eggs there was formed by nuclear proliferation an evident syncy- 

 tium, and that from this there was later a differentiation of the 

 embryonic tissues without the process of ordinary cleavage. I 

 have found something of the same kind in the case of Clara. 

 Occasionally an egg was found among serial sections which 

 showed no evidence of cytoplasmic cleavage, but where internal 

 nuclear proliferation was clearly evident, and the specimens were 



15 



FIGS. 10-18. Outline sketches of sections of single egg, showing the various dis- 

 tribution of nuclei, shape of egg, etc. 



numerous enough to enable one to definitely determine the phases 

 of tissue differentiation and the formation of the embryo. In these 

 cases were found the same evidences of the origin and organiza- 

 tion of nuclei dc novo which were found in Eudendrium and Pcn- 

 naria. It was possible to trace almost every phase of this nu- 

 clear organization, from the appearance of the smallest particles of 

 chromatin and their segregation into larger masses to the fully 

 formed resting nucleus with its typical elements in normal rela- 

 tions and proportions. 



- linitosis and Nuclear Organization. During the early cleav- 

 age, even up to the sixteen-cell stage, no evidence of mitosis has 



