62 ^ The Unity of the Organism 



the polyp-generation from which place those cells make their 

 journey to the ectoderm of the medusa, usually to some 

 portion of it connected with the manubrium or digestive 

 part of the animal. But — and here we come to the real 

 point of the present discussion — since sex-cells are found by 

 actual observation in the endoderm, in several genera and 

 species, the theory is that the Marschroute lies first in the 

 ectoderm, then passes over into the endoderm and returns 

 later to the final goal of the sex-cells in the manubrial ec- 

 toderm. The ectoderm therefore is the home by natural- 

 ization, so to say, of the germ-plasm in these animals ; it is 

 originally planted there from the parental egg and finally 

 matured there. As will be seen from what has previously 

 been said, the kernel of the theory is to account for the 

 positions and movements of the sex-cells in accordance with 

 the supposition that their most essential part, their genri- 

 plasm, cannot be formed anew from somatoplasm of any 

 sort either entodcrmal or ectodermal, but must come over 

 in direct continuity from the germ-plasm of the parental 

 egg. The reason why the theory is so insistent on ascrib- 

 ing the sex-cells to the ectoderai is that it supposes that 

 originally in the evolutional history of the group,, the germ- 

 plasm destined for the next generation of sex-cells was 

 lodged in the ectoderm, and that this predestined it to that 

 layer for all time. 



Inconclusive ness of Weismanns Results Shown hy Goette 



and Others 



We have now to inquire how it has fared in later research 

 with the numerous subsidiary hypotheses which enter into 

 this complex tlieory of germ-plasm behavior in these organ- 

 isms. Alexander Goette has lately gone over almost the 

 entire grounds covered by Weismann in tlio monograph al- 

 ready mentioned, and his i*esults and general conclusions 



