Statement of Weismann s System (1886). 15 



which originally led to sexual reproduction is at 

 present a matter that awaits suggestion by way of 

 hypothesis ; and, therefore, it now only remains to add 

 that the general structure of Professor Weismann's 

 system of hypotheses leads to this curious result — 

 namely, that the otherwise ubiquitous and (as he 

 supposes) exclusive dominion of natural selection 

 stops short at the protozoa, over which it cannot 

 exercise any influence at all. For if natural selection 

 depends for its activity on the occurrence of congenital 

 variations, and if congenital variations depend for 

 their occurrence on sexual modes of reproduction, it 

 follows that no organisms which propagate by any 

 other modes can present congenital variations, or thus 

 become subject to the sway of natural selection. 

 And inasmuch as Weismann believes that such is the 

 case with all the protozoa, as well as with all 

 parthenogenetic organisms he does not hesitate to 

 accept the necessary conclusion that in these cases 

 natural selection is without any jurisdiction. How, 

 then, does he account for individual variations in 

 the protozoa ? And, still more, how does he ac- 

 count for the origin of their innumerable species ? 

 He accounts for both these things by the direct 

 action of external conditions of life. In other words, 

 so far as the unicellular organisms are concerned, 

 Weismann is rigidly and unconditionally an advocate 



on the advantage which it affords to the operation of natural selection. 

 .... Sexual reproduction has arisen by and for natural selection as the 

 sole means by which individual variations can be united and combined 

 in every possible proportion." — Nature, vol. xli. p. 322. 



How such contradictory statements can be reconciled I do not 

 perceive ; but they furnish a good example of the extreme laxity with 

 which the term " natural selection " is used by ultra-Darwinians. 



