26 fHE COMING OF MAN 



compete directly with the large and powerful vertebrate. 

 More important still small size seems to be usually correlated 

 with short hfe. The life of the full-grown insect rarely 

 exceeds a few months and is, as a rule, much briefer 

 than this. The larger vertebrates live for several or many 

 years. 



A brief span of life is not productive of intelligence born of 

 long, oft repeated, but varying emergencies and experiences. 

 There is little opportunity for the individual to learn thereby. 

 In the rapidly recurring and succeeding generations successful 

 habits, or mental peculiarities quickly become fixed, and are 

 handed down practically unchanged as inherited instincts. 

 There is little stimulus or opportunity for mental growth in 

 an animal whose whole experience is limited to a few months 

 of easy and enjoyable summer. The whole subject of instinct 

 and intelligence, their resemblance and differences, compen- 

 sating advantages and disadvantages, especially their origin, 

 forms a field of most fascinating study, into which we will not 

 attempt to enter. 



We can only glance at the early individual development of 

 insects. Excepting a very few of the most primitive, they all 

 attain their adult form through a metamorphosis most marked 

 and complete in the highest and latest forms. The butterfly 

 is born a caterpillar, the bee a sort of grub, the fly a maggot. 

 The advantage of the metamorphosis is evident. We have 

 seen that every egg must contain enough nourishment to feed 

 the embryo until it reaches a stage where it can shift for itself, 

 and the simpler the animal at birth, the shorter the embryonic 

 life, and the less nourishment required in the egg. 



Out of a given amount of surplus material to be devoted to 

 reproduction, a few large eggs or many smaller ones can be 

 formed. It is a great advantage to the species that the eggs 

 should be as numerous as possible, and that to gain this advan- 

 tage the young are born in as simple and incomplete a form 

 and as quickly as possible. Hence the butterfly is born in a 

 caterpillar stage, and must gather, assimilate and store up 



