GERM CELLS OF COELENTERATES 49 



the theory, that it may be questioned whether the theory appHes 

 at all extensively to animals of any phylum. 



As a rule, those coelenterate eggs which secure nourishment 

 from the adjoining enteric cavity have large nuclei; and the 

 ones which absorb oocytes or other cells possess relatively small 

 nuclei. Whether this correlation be incidental, or whether it 

 have a deeper significance, is not known. 



Cytoplasmic granules which stain in nuclear dyes are a char- 

 acteristic feature of coelenterate eggs. Typically, these appear 

 in young oocytes about the time growth begins, and they may 

 also form at other times during growth. From their initial posi- 

 tion, close to the nuclear wall; from their staining reactions; 

 from the behavior of other cytoplasmic and nuclear substances; 

 the author has interpreted these granules as chromatin. Ob- 

 servations by other investigators, upon the eggs of other 

 animals, have led them to conclude that chromatin does migrate 

 into the cytoplasm. The criticism that the usual tests for 

 chromatin are not specific is justified in large measure, but 

 digestive experiments have demonstrated the presence of nucleic 

 acid compounds in cytoplasmic granules, similar to those de- 

 scribed for coelenterate eggs. Also van Herwerden has observed 

 a migration of nuclear material into the cytoplasm of living 

 oocytes of Echinoderms. Using these experiments to check the 

 other observations, it seems probable that the cytoplasmic 

 bodies described as chromatin do, in fact, represent this sub- 

 stance. There is considerable diversity of opinion as to the 

 functions of these inclusions, and further work is necessary to 

 determine this with certainty. 



The chromosomes of most coelenterates do not lend themselves 

 to a study of details of behavior to the degree possible in some 

 animals. This is due, chiefly, to the lack of variety in form and 

 size. It is not possible, therefore, to determine whether the 

 chromosomes reappear in each generation in precisely the same 

 form and size they had in earlier generations. During inter- 

 kinesis the nucleus is a single vesicle with no subdivisions into 

 smaller vesicles, and the chromatin is in the form of a continuous 

 reticulum. 



