273 



of the same scale of magnification. Great care has been taken to 

 select only those cases which appeared perfectly clear and convincing. 

 The distribution of chromatic and achromatic substances within the 

 nucleus is indicated in the figures. 



Observations. 

 Coelentera. 

 Tubularia mesembryanthemum. In 1903 I was struck 

 by the apparent absence of mitosis in the developing hydranths on 

 pieces of Tubularia stems. Examination of the sections in various 

 stages of regulation showed numerous amitoses and very few mitoses 

 in all except the earliest. In Figure 1, a few of the observed cases are 





II 



Fig. 1. 



shown. Nos. I — VII are from the ectoderm, Nos. VIII— X from the 

 entoderm. The question as to whether cell-division occurs after nuclear 

 division is very difficult to settle by observation, but if it does not, a 

 large number of cells containing two or more nuclei should be found, 

 since amitosis is so common. Search for such cells resulted in the 

 discovery of only two or three. I am forced, therefore, to conclude 



Anat. Anz. XXX. Aufsätze. 



18 



