The Animal Organism and its Germ-Layers 67 



a bud is to form, migrates into the endodcrm, and so ex- 

 plains the participation of the endoderm in bud production. 

 Goette's conclusions as to the actual endodermal origin 

 of sex-cells in the hydroids are not unsupported by other 

 workers. Tlius Tichomiroff liolds that the sperm cells of 

 Kudcndritun (uircntuim arise in this layer, and C. W. Har- 

 gitt, who has devoted much time to the question, is unquali- 

 fied in his statements. He writes in a summary presentation 

 of his results : "It may be said that while in Eudendrium 

 ramosum and E. tenue the ova arise strictly in the endo- 

 derm, and never at any time find their way into the ectoderm, 

 in the species racemosum and diapar these products are 

 found abundantly in both tissues." So the observations 

 seem conclusive that taking the group of hydromedusae as 

 a whole, the sex-cells arise in the ectoderm in some species 

 and in the endoderm in other species, and that this origina- 

 tion is by a transformation of substance in both cases from 

 what it was originally into that of the reproductive elements. 

 Indeed the power of the propagative function of the organ- 

 ism to start indifferently with either cctodcrmal or endo- 



ermal material and reach the same end as seen in different 

 genera of the hydromcdusa>, seems in some cases to extend 

 to different species of the same genus. "If one holds rigor- 

 ously to the facts," writes Goette, "he must in spite of all 

 hold to it as most probable that the Kewnst'dtte in different 

 species of Etifft'inlriHnt, perhaps indeed in the same spe- 

 cies, changes." J1 



Finally, and as a cap-sheaf to the arguments here pre- 



nted in favor of the view that sex-cells do arise genuinely 

 anew in each individual in the hydromedusa?, it remains to be 

 shown that Weismann himself was really in accord with 

 Goette on this point when he wrote the monograph on the 

 origin of the sex-cells ; and that only later under the impul- 

 sion of his speculations about germ-plasm did he come to 

 repudiate this view. On page 284 of the monograph we find 



