74 An Examination of Weismannism. 



Darwin — still less, of course, between his theory and 

 that of Galton. Lastly, in this connexion we ought 

 to remember that the Hydromedusae are organ- 

 isms in which the specialization in question happens 

 to be least, as is shown by the fact that entire indi- 

 viduals admit of being reproduced from fragments of 

 somatic-tissues ; so that these are organisms where 

 we would least expect to meet with the migration 

 of germ-cells, were the purpose of such migration 

 that which Weismann suggests. This line of evidence 

 therefore seems valueless. 



Nor does it appear to me that the second line of 

 evidence is of any more value. In the first place, 

 there is no shadow of a reason for supposing that an 

 apparently anatomical isolation of germ-cells neces- 

 sarily entails a physiological isolation as regards 

 their special function — all "physiological analogy," 

 indeed, being opposed to such a view, as is shown 

 in Appendix I. In the second place, there is no 

 proof of any anatomical isolation, as we may like- 

 wise see in that Appendix. In the third place, the 

 fact relied upon to indicate such an isolation — viz., 

 the early formation of germ-cells — is not a fact of any 

 general occurrence. On the contrary, it obtains only 

 in a comparatively small number of animals, while it 

 does not obtain in any plants. In the Vertebrates, 

 for example, the reproductive cells are not dif- 

 ferentiated from the somatic cells till after the em- 

 bryo has been fully formed ; while in plants their 

 development constitutes the very last stage of onto- 

 geny. In the fourth place, the argument, even for 

 what it is worth, is purely deductive ; and deductive 

 reasoning in such a case as this — where the phonemena 



