THE WEAK SIDES OF NATURAL SELECTION. 83 



As regards the "volley of questions" with which the Darwinian' 

 is assailed we all know that any theory must stand or fall 

 according to the questions it can solve. If Nature — I dislike the 

 term — has been for millions of years ever striving to improve 

 plants and animals, preserving only modifications which are useful 

 to them and cancelling every step in a different direction, it might 

 be expected that the peculiarities which I pointed out would have 

 been on the way to extinction. Darwinism says that every useless 

 feature in an animal is a drain on its resources by which it must be 

 pro tanto handicapped in the "struggle for existence." The 

 illustration from the ship-building yard seems to me singu- 

 larly unhappy. The uses to which iron and steel are there put 

 are purely mechanical, and the question raised by the supposed 

 visitor as to its chemical constitution is therefore irrelevant. But 

 the difficulties which I have ventured to point out are of the very 

 essence of the question. 



The position of the shark's mouth is undeniable, and all evidence 

 agrees to show that it is an inconvenience. Granted that the loss 

 of time to the shark is small, yet the delay of a second may turn 

 the scale between life or death. Unless the peculiarity of the 

 shark's mouth is a gain to this fish it ought not, on the principle 

 of Natural Selection, to have been preserved. 



After careful inquiry made both before drawing up my paper and 

 subsequently, all the observations I have been able to meet with 

 agree with the view that the position of the shark's mouth is and 

 must be a disadvantage. 



The distinction between an enemy and a competitor is, in the 

 instance given, purely nil, as far as the species attacked is con- 

 cerned. 



Mr. Murphy, in contending that this difference is something 

 real, forgets that to the sheep it makes no ultimate difference 

 whether it is devoured by wolves or starved from want of food. 

 Nor does it differ substantially from the naturalist's point of 

 view, since one and the same end is effected though in another 

 manner. 



The Rev. Dr. Walker's critique is most valuable. He regards 

 the question — or questions — with the eye of a practical observant 

 naturalist and points out some of the many difficulties to be 

 encountered in explaining, e.g., the colouration of insects. 



It is, indeed, possible that the chlorophyll of green vegetables 

 may take a part in the colouration of butterflies. But we have to 

 ask why are green colours wanting in other species which select 

 the same diet ? 



I have succeeded in detecting tannin in many insects — all 

 plant-feeders — and I think this fact may explain the frequent 

 occurrence of browns, russets, tans, &c, both in Lepidoptera and 

 Coleoptera. But before we can generalise we must acquire a 



