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, 



