ZOOGENESIS 



stances — is common to nearly all insects which have 

 an inactive helpless pupal stage. 



Among the birds mental attributes which parallel 

 the human are almost exclusively confined to those 

 types with helpless young which for their upbringing 

 require the constant attention of both parents, and 

 among these they are most obvious and marked in 

 the smaller and weaker forms such as the tailor and 

 the weaver-birds and in the wrens and swallows. 

 Birds with active and more or less self-reliant young 

 which are tended by one parent only, large and power- 

 ful birds, and sea-birds nesting where they are safe 

 from enemies, as a rule show little or no skill in 

 making nests and scorn the use of ornaments. 



Weak and helpless young are especially character- 

 istic of the rodents, particularly of the small mouse- 

 like or rat-like rodents, in which the man-like mental 

 attributes are particularly to be remarked. 



The nests of rodents, like the nests of birds, are 

 primarily incubators designed to facilitate the main- 

 tenance of a proper temperature. Many rodent nests, 

 as those of various mice, the muskrats, and some 

 squirrels, would seem to be constructed in such a 

 fashion as to create within them a temperature higher 

 than that outside through bacterial action. Whereas 

 among the birds nests are used only as incubators for 

 the young, many northern rodents pass the winter 

 in their nests in a state of hibernation. Correspond- 

 ingly in Madagascar some lemurs pass the hot dry 

 season in their nests in a state of aestivation. 



So a survey of the animal world seems to point to 



