PSYCHICAL EVOLUTION 115 



all as much alike as the multitudes on an ant-hill. 

 The Peckhams of Milwaukee, those indefatigable 

 investigators of spiders and insects, are constantly 

 telling us of the wonderful individuality possessed 

 by these lowly lessees of our fields and gardens. 

 In their work on ' The Plabits and Instincts of the 

 Solitary Wasps,' speaking of the ammophiles, these 

 authors say : ' In this species, as in every one that 

 we have studied, we have found a most interesting 

 variation among the different individuals, not only 

 in methods, but in character and intellect. While 

 one was beguiled from her hunting by every sorrel 

 blossom she passed, another stuck to her work 

 with indefatigable perseverance. While one stung 

 her caterpillars so carelessly and made her nest in 

 so shiftless a way that her young could survive 

 only through some lucky chance, another devoted 

 herself to these duties not only with conscientious 

 earnestness, but with an apparent craving after 

 artistic perfection that was touching to see.' The 

 variation in the mental phenomena of animals, 

 including man, is partly innate, and partly the 

 result of environment or education. 



Animals not only vary in their mental qualities, 

 but they also inherit these variations, just as they 

 do physical properties and peculiarities. Evidence 

 of this is furnished by every new being that 

 comes into the world. Insanity runs in fami- 

 lies, and so does genius and criminality. Even 

 the most trifling idiosyncrasies are often trans- 

 mitted, not only by men, but also by dogs, horses, 

 and other animals. Such qualities of mind as 



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