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 
