422 
DARWINISM 
CHAP. 
these American evolutionists have departed very widely from 
the views of Mr. Darwin, and in place of the well-established 
causes and admitted laws to which he appeals have introduced 
theoretical conceptions which have not yet been tested by 
experiments or facts, as well as metaphysical conceptions 
which are incapable of proof. And when they come to 
illustrate these views by an appeal to palaeontology or 
morphology, we find that a far simpler and more complete 
explanation of the facts is afforded by the established principles 
of variation and natural selection. The confidence with which 
these new ideas are enunciated, and the repeated assertion 
that without them Darwinism is powerless to explain the 
origin of organic forms, renders it necessary to bestow a little 
more time on the explanations they give us of well-known 
phenomena with which, they assert, other theories are incom¬ 
petent to grapple. 
As examples of use producing structural change, Mr. Cope 
adduces the hooked and toothed beaks of the falcons and the 
butcher-birds, and he argues that the fact of these birds belong¬ 
ing to widely different groups proves that similarity of use has 
produced a similar structural result. But no attempt is made 
to show any direct causal connection between the use of a bill 
to cut or tear flesh and the development of a tooth on the 
mandible. Such use might conceivably strengthen the bill 
or increase its size, but not cause a special tooth-like outgrowth 
which was not present in the ancestral thrush-like forms of 
the butcher-bird. On the other hand, it is clear that any 
variations of the bill tending towards a hook or tooth would give 
the possessor some advantage in seizing and tearing its prey, 
and would thus be preserved and increased by natural selection. 
Again, Mr. Cope urges the effects of a supposed “ law of polar 
or centrifugal growth ” to counteract a tendency to un- 
symmetrical growth, where one side of the body is used more 
than the other. But the undoubted hurtfulness of want of 
symmetry in many important actions or functions would 
rapidly eliminate any such tendency. When, however, it has 
dress, namely, what is the meaning and importance of Professors Cope and 
Hyatt’s views on acceleration and retardation ? I have endeavoured, and 
given up in despair, the attempt to grasp their meaning ” {Life and Letters , 
vol. iii. p. 233). 
