872 The American Naturalist. [April, 
Wallace and Poulton, are well taken. While he is far from denying 
the efficacy of that process, he does not trace to it the origin of char- 
acters, and he presents various instances where the latter seem to have 
een the consequence of the direct action of physical causes. His 
investigations are especially valuable because they cover a field which 
has been especially cultivated by the advocates of the exclusive effi- 
ciency of natural selection, and he thus throws new light on the class 
of facts where the evidence for natural selection is strongest. For 
this reason the work will well repay perusal, as it serves as a corrective 
to thought which has, in the opinion of many, gone to an extreme in 
one direction. 
Ñ 
Fic, 1. The Stoat in winter pelage, or Ermine. 
The author cites the following remarkable example of the direct 
effect of physical causes in producing changes of coloration : 
“That the yellow color of canaries can be altered to an orange red 
by mixing cayenne pepper with their food has been known for a long 
ime. This curious fact was first discovered in England, as was also 
the fact that the different races of canaries vary in their susceptibility 
to the action of the pepper; some kinds are more, others are less 
affected, while one race is absolutely without any power of having its 
coloration altered by these means. The color change is produced by 
feeding the newly hatched young with the pepper conveyed in their 
food or the old birds while sitting upon the nest are furnished with 
food containing the cayenne, which they in turn feed their offspring. 
The color change can, in fact, be only brought about in very young 
