134 THE EVOLUTION OF INSTINCT 
origin, but it is a suggestive fact that the same trait in vary- 
ing degrees occasionally crops out in other varieties of mice, 
and Haake has described a similar curious variation in a 
species of shrew. Hereditary peculiarities of movement 
have been described many times both in man and in animals. 
Darwin quotes an account communicated by the Rev. W. 
Darwin Fox of a terrier which when begging moved her 
paws in a very peculiar manner very different from that of 
other dogs; “her puppy, which never could have seen her 
mother beg, now when full grown performs the same peculiar 
movement exactly in the same way. Another peculiar he- 
reditary variation is reported in a letter by Dr. Huggins to 
Darwin, of an English mastiff which when first taken out, 
at the age of six weeks, from the house where he was born 
started back in alarm at the first butcher shop he had seen. 
Later when the endeavor was made to get him past the 
butcher shop he threw himself down and could not be induced 
by coaxing or threats to pass the shop. On enquiry it 
was found that the same peculiar antipathy was possessed by 
the father of the dog, by the grandfather and by two others 
of the latter’s descendants 
Illustrations of variations in instinctive behavior might 
be multiplied almost indefinitely, but what has been said will 
perhaps suffice to give some indication of the prevalence 
of such variation throughout the animal kingdom. So far 
as can be determined, variations of instinct have little regard 
to utility; they may be of service to their possessors, or, 
like Huggins’ case of the inborn aversion of a dog to butcher 
shops, of no particular value, or positively injurious as in 
the occasional deterioration of the instinct of incubation. 
As instincts are no less important than corporeal structures 
in the struggle for existence, we can readily conceive how 
useful variations may be accumulated by natural selection, 
