4 GEORGE T. HARGITT 



differentiation of cells of either one or both the entoderm and 

 ectoderm." Growth takes place in the position where they are 

 formed through the nutritive activities of surrounding cells, and 

 a migration toward the gonophore region is also characteristic. 

 It is suggested that the presence of germ cells in a certain region 

 may act as a stimulus to the production of gonophores. Goette 

 ('07), studying E. rameum and E. racemosum, found the smallest 

 germ cells in the ectoderm, and he looks upon this as the seat 

 of formation of germ cells in Eudendrium. From his work on 

 various hydroids he is convinced that the place of origin of 

 germ cells in these organisms is a varied one in different species 

 or even in the same species; i.e., the germ cells may sometimes 

 arise in the ectoderm and sometimes from the entoderm, even in 

 the same species. 



In regard to the formation of male germ cells, Ciamician 

 ('78) believes the sperm mother cells arise by transformation of 

 entoderm cells within the gonophore. It may be doubted 

 whether his conclusions can be considered really to touch the 

 matter of ultimate origin; his figures do not give this impression. 

 Weismann ('83) is of the opinion that they arise not in the gono- 

 phore, but in the stalk of the hydroid and later migrate into the 

 gonophore. He confirms Ciamician on their entodermal origin. 

 Goette ('07) sees the ectoderm as the point from which the 

 sperm cells as well as the egg cells come. 



These are the chief papers dealing with the facts of germ-cell 

 formation in Eudendrium. Other papers are found which dis- 

 cuss the facts without adding any observations or new facts. 

 Weismann ('04) discusses Eudendrium and its germ cells along 

 with other hydroids and here takes the positive ground, con- 

 trary to his own earlier brilliant observations, that the germ 

 cells of Eudendrium and of all Hydromedusae arise in the ecto- 

 derm. This is apparently a necessary assumption for him, since 

 his thesis of the distinctness and self-perpetuation of the ger- 

 minal substance requires more constancy of germ-cell position 

 than the observed facts present. The same hypothesis also in- 

 volves germ-cell formation early in the development of the 

 hydroid and an unbroken line of such cells up to the time of the 



