IS THE THEORY OF SELECTION SUFFICIENT? I37 



point of Physiolog-y and the Theory of Descent (Das 

 Unbewusste vom Standpunkt der Physiologie and Dcs- 

 cendenztheorie)/® has again recently observed that the 

 truth of the doctrine of Descent is independent of tlic 

 bearings and adequacy of the Darwinian theory. 



" This circumstance," he says, " is misunderstood by 

 the majority of Darwin's opponents ; when they adduce 

 arguments for the inadequacy of natural selection in 

 the struggle for life, they usually fancy they have 

 adduced just as many arguments against the reliability 

 of the theory of Descent. But the two have no direct 

 connection with one another ; for it might be possible 

 that Darwin's theory of natural selection was absolutely 

 false and unserviceable, and the doctrine of derivation 

 true notwithstanding ; that only the causal medium of 

 the derivation of one species from another was different 

 from that stated by Darwin. Similarly, it might be 

 possible that, although the mediate causes of transition 

 discovered by Darwin were partially effective, — on the 

 other hand, transitional phenomena existed which could 

 not as yet be explained by this hypothesis ; that this 

 therefore required either an auxiliary hypothesis supple- 

 menting that of Darwin, or even a co-ordinating prin- 

 ciple of explanation, as little discovered now as was the 

 Darwinian theory twenty years ago. Such imperfect 

 knowledge of the causes operating in the transition of 

 one form into the other, can prejudice the general 

 truth of the doctrine of Descent as little as the absence 

 of intermediate forms, or the uncertainty, still exist- 

 ing in many cases, of the derivation of any given form. 

 If even in former times, when all knowledge of the 

 causes by which transition is effected was still wantin 



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