126 
Rev. J. T. Gulick on the 
confining our attention to Mr. Wallace’s very interesting and 
suggestive volume on c Darwinism ’ we shall be better able to 
judge of the possibility of producing a self-consistent theory 
on this basis ; but we should bear in mind that the same view 
is maintained by many naturalists, and that parallel statements 
abound in their writings. Mr. Wallace’s volume not only 
embodies the mature reflections of one of the joint authors of 
the theory of natural selection, but it fairly represents that 
phase of biological theory which considers diversity of natural 
selection through exposure to different environments the only 
cause of divergence. The following passage will show the 
exclusive nature of his theory : — u A great body of facts on 
the one hand and some weighty arguments on the other alike 
prove that specific characters have been and could only have 
been developed and fixed by natural selection because of their 
utility. We may admit that among the great number of 
variations and sports which continually arise many are alto- 
gether useless without being hurtful ; but no cause or influ- 
ence has been adduced adequate to render such characters 
fixed and constant throughout the vast number of individuals 
which constitute any of the more dominant species ” (* Dar- 
winism/ p. 142). This is in strong contrast with the follow- 
ing passage from the close of the Introduction of the sixth 
edition of the c Origin of Species/ which is the last one that 
received the revision of the author : — “ I am fully convinced 
that species are not immutable, but those belonging to what 
are called the same genera are lineal descendants of some 
other and generally extinct species, in the same manner as 
the acknowledged varieties of any one species are the descen- 
dants of that species. Furthermore I am convinced that 
Natural Selection has been the most important, but not the 
exclusive, means of modification.” On page 421 of the same 
edition Darwin calls attention to the fact that this passage 
has u been placed in a most conspicuous position ” in the 
different editions of his work, and complains of the writers 
who misrepresent his conclusions on this point. 
Facts that are neglected or denied . 
Though Darwin maintains that besides the inherited effects 
of use and disuse and the direct action of the external con- 
ditions there are other forms of variation leading to permanent 
modifications of structure independently of natural selection 
( ( Origin of Species/ 6th London ed. p. 421), he does not 
attempt to explain how these divergences arise. Neither 
Darwin nor AYallace appears to have observed that, as in 
domestication, the isolated breeding of other than average 
