88 GEORGE T. HARGITT 



case in these two species, but it might be expected that closely 

 related forms would show the same thing. But no one who has 

 studied these or similar forms, whether European or American 

 species, has described or claimed such an early differentiation, 

 save the two authors mentioned. In the descriptions of both 

 Harm and Wulfert the only evidence presented for identifying 

 certain cells as primordial germ cells was the appearance of the 

 cytoplasm, and I have shown that by itself such evidence is not 

 conclusive and is apt to lead one into error. The figures of these 

 two authors are not sufficiently clear to show whether other 

 characteristics are apparent. 



In Campanularia flexuosa, Tubularia crocea, Pennaria tiarella, 

 Hybocodon prolifer, Cyanea arctica, Aurelia flavidula and other 

 coelenterates I have examined the developing egg and larva 

 without finding germ cells, though there are some cells which 

 may have some resemblance to germ cells. In Clava leptostyla 

 I have examined young and old polyps, young and old gono- 

 phores, and various stages in the development of the egg, and 

 only when the gonophores are about to form, or have formed, 

 are germ cells present. When present, such cells are found only 

 in the pedicel of the gonophore or in the wall of the hydranth 

 close to the gonophore stalk. Furthermore, in no case has it 

 been possible to identify germ cells until they have the charac- 

 ters already enumerated as diagnostic. This is, of course, clearly 

 understandable in those cases where germ cell are derived by 

 division from the general epithelial surface; in such cases the 

 germ cells are not present before this period. Also in Canipanu- 

 laria and others, where the eggs develop within closed gonophores, 

 there are few interstitial cells, gland cells, or nematocysts and 

 consequently nothing to render the germ cells indistinct, or to 

 confuse with them. Under such conditions there is slight chance 

 of missing any germ cells which might be present, and their 

 absence is therefore good warrant for denying any early differ- 

 entiation and segregation. In the forms mentioned as having 

 come within my own observation I am confident that germ cells 

 are not recognizable in such early stages of development as 

 claimed by Wulfert and Harm. I have a feeling of skepticism. 



