560 
Mr. Spencer says that the introduction of new organs 
could not be explained by the principle of the inherited 
effects of use and disuse, and he therefore infers that this 
phenomenon must have been brought about by Natural 
Selection. But, as we have already shown, the evolution 
of the electric organ in certain fishes cannot be explained 
on the principles of Natural Selection. On the contrary, 
it is readily admitted that it offers the greatest difficulty to 
the acceptance of the theory. 
Mr. Spencer argues that:— 
“ the relations of tendons to bones and to one another, are not always 
the same. Variations in their modes of connection may occasionally 
prove advantageous, and may thus become established. Here again, 
then, we have a class of structural changes to which Mr. Darwin’s 
hypothesis gives us the key, and to which there is no other key.”— 
(p. 8.) 
I am in ignorance of the precise nature of the facts 
from which Mr. Spencer draws this very important in 
ference. But we may remark that the case, as put by 
Mr. Spencer, is altogether hypothetical. He does not 
prove that some of these variations must be useful ; he 
simply asserts that they may be useful. But they must be 
useful—they must secure the survival of those who possess 
these modifications, while the others, not so modified, are 
destroyed—if they are to be referred to a class of structural 
changes to which Mr. Darwin’s hypothesis gives us the 
key. 
And then, what are we to say as to the assertion that 
there is no other key than that of Natural Selection to 
explain this phenomenon. What is the phenomenon ? 
“ The relations of bones to tendons are not always the 
same.” That, I suppose, means that the tendons are not 
always attached to exactly the same point. But the fact 
that such variations are to be found, seems to indicate that