1 6 An Examination of Weismannism. 



of the theory of Lamarck — just as much as in the case 

 of all the multicellular organisms he is rigidly and un- 

 conditionally an opponent of that theory. Nevertheless, 

 there is here no inconsistency : on the contrary, it is 

 consistency with the logical requirements of his theory 

 that leads to this sharp partitioning of the unicellular 

 from the multicellular organisms with respect to the 

 causes of their evolution. For, according to his view, 

 the conditions of propagation among the unicellular 

 organisms are such that parent and offspring are one 

 and the same thing ; " the child is a part, and usually 

 a half, of its parent." Therefore, if the parent has 

 been in any way modified by the action of external 

 conditions, it is inevitable that the child should, from 

 the moment of its birth (i.e., fissiparous separation), 

 be similarly modified ; and if the modifying influences 

 continue in the same lines for a sufficient length of 

 time, the resulting change of type may become 

 sufficiently pronounced to constitute a new species, 

 genus, &c. But in the case of the multicellular or 

 sexual organisms, the child is not thus merely a 

 severed moiety of its parent ; it is the result of the 

 fusion of two highly specialized and extremely minute 

 particles of each of two parents. Therefore, whatever 

 may be thought touching the validity of Weismann's 

 deduction that in no case can any modification induced 

 by external conditions on these parents be trans- 

 mitted to their progeny, at least we must recognize 

 the validity of the distinction which he draws between 

 the facility with which such transmission must take 

 place in the unicellular organisms, as compared with 

 the difficulty— or, as he believes, the impossibility — 

 of its doing so in the multicellular. 



