930 | The American Naturalist. [October, 
small a degree, and to illustrate by new examples, the great principles 
of biology enunciated by Darwin, and in especial “the preéminent 
principle ’’ of natural selection. 
To the above general description of Mr. Poulton’s work, which we 
take, with some alterations, from a contemporary, we add the follow- 
ing comments: 
The author remarks in his preface: ‘‘ It is common enough nowa- 
days to hear of new hypotheses which are believed (by their inventors) 
to explain the fact of evolution. These hypotheses are as destructive 
of one another as they are supposed to be of natural selection, which 
remains as the one solid foundation upon which evolution rests. ? 
this book is a conspicuous example of the type of thought which 
regards natural selection as the cause of evolution, we give some atten- 
tion to its method of treatment of this interesting question. This 
treatment consists, as in the case of other post-Darwinians, as Wallace, 
Lankester, etc., in a failure to consider the problem of the origin 
of the variations between which there is a struggle for existence, and 
which are therefore the materials of natural selection. It would appear 
that these scientists are generally insensible to the fact that there is 
any such question. I say generally, for occasionally each of them 
slips into an attempt to assign some physical or mechanical cause to 
a variation. The question will not down, as is illustrated in several 
places in Mr. Poulton’s book. One which cannot be avoided is the 
question of the origin of significant colors, where our author, in one 
short sentence, ‘‘ gives away’’ the whole question. On page 13 he 
remarks: ** All animal color must have been originally non-significant, 
for although selective agencies have found manifold uses for color, 
this fact can never have accounted for its first appearance." The 
prompt avoidance of the question of origin, however, immediately 
follows, as he goes on to say: ‘It has, however, been shown that this 
first appearance presents no difficulty, for color is always liable to 
occur as an incidental result." We should like to know something 
about the origin of color and its distribution in animals, but of this 
we find scarcely a hint in the entire book. On the other hand, the 
book consists of full and rich illustrations of the utility of color shades 
and patterns after they have been produced. 
The question of mimicry is fully illustrated and. discussed, and the 
conclusion is reached that its existence can be fully explained by 
natural selection. The real question of the origin of mimetic color- 
ation is not considered, except in a foot-note on page 224. 
? The italics are our own. 
