EVOLUTIONS OF ORGANIZATION. 21 



us, explain it as you will, in full functional opera- 

 tion. But even supposing, as seems possible 

 enough, that vertebrates possessing vision were 

 once linked to forms like larval ascidians by ani- 

 mals of soft structure with gradually increasing 

 perfection of sight, and that amphioxus is after 

 all degenerated from some member of such a lost 

 chain of transitional forms, the visually useless 

 stages of development of the vertebrate eye 

 cannot be the mere accumulated record of a 

 series of gradually improving optical instru- 

 ments. 



No more than Lamarck has Darwin considered 

 that it is not a sensitive nerve alone which is 

 required to begin vision or any other special sense, 

 but a capability of the consciousness to be modified 

 in a way altogether incomparable with the equally 

 incomprehensible affection which constitutes gen- 

 eral sensation. 



While the Darwinian system adds the idea of 

 natural selection to the stock of hypotheses for 

 explanation of evolution by external influences, it 

 denies the existence of any definite evolution of 

 organization dependent on a definite cause. While 

 it has the greatest faith in the power of the ovum 

 to carry down the most minutely determined 

 details of future development, it denies that there 



