14 LIVERPOOL BIOLOGICAL SOCIETY. 
upper surface of the Doris was of precisely the same colours 
arranged in the same way, so that one could look at it for 
some little time as it lay in the pool before becoming aware 
that it was other than a part of the surrounding rock. My 
companion and I were both greatly struck by the closeness 
of this mimetic resemblance to the surrounding colouring. 
We picked up the Doris and remarked the brightness and 
the unusual character of its markings, and then replaced it 
upon the rock, when it once more became inconspicuous. 
Now, there can be no doubt that this protective resem- 
blance was not accidental. It must have been brought 
about by some modifying influence, but in answer to the 
question as to what influence had been at work, two sets 
of evolutionists might give very different answers. The one 
set of philosophers might say the colouring of this Doris is 
evidently the result of the direct action of the environment; 
while another set would argue that the condition has been 
brought about by natural selection acting upon congenital 
variations produced purely as the result of heredity; and I 
do not see how, in the present state of our knowledge, an 
impartial judge could decide which was the correct theory. 
My own impression, which, however, I cannot support 
by any evidence, is that probably both processes were at 
work in the evolution of this and similar peculiarly coloured 
specimens. I believe in natural selection as being the 
most powerful and most constantly acting of the factors, 
but I think it probable that some influence is exercised 
directly by the environment, perhaps in the way of 
producing non-inherited variations in the most advan- 
tageous direction, which are then picked out by natural 
selection. But in order to settle this and many similar 
questions in the philosophy of Biology, it would be 
necessary to carry out a series of carefully devised 
experiments, extending over a number of generations. 

