6 THE LIFE-STORY OF INSECTS [CH. 



the insect spends a period as a pupa (fig. 1 e) unable 

 to move from place to place, and taking no food. 



Such, in brief, is the course of the most familiar of 

 insect life-stories. For the student of the animal 

 world as a whole, this familiar transformation raises 

 some startling problems, which have been sugges- 

 tively treated by F. Brauer (1869), L. C. Miall (1895), 

 J. Lublx)ck (1874), R. Heymons (1907), P. Deegener 

 (1909) and other writers 1 . To appreciate these prob- 

 lems is the first step towards learning the true 

 meaning of the transformation. 



The butterfly's egg is absolutely and relatively of 

 large size, and contains a considerable amount of 

 yolk. As a rule we find that young animals hatched 

 from such eggs resemble their parents rather closely 

 and pass through no marked changes during their 

 lives. A chicken, a crocodile, a dogfish, a cuttlefish, 

 and a spider afford well-known examples of this rule. 

 Land-aiiimala, generally, produce young which are 

 miniature copies of themselves, for example horses, 

 dogs, and other mammals, snails and slugs, scorpions 

 and earthworms. On the other hand, metamorphosis 

 among animals is associated with ei^s of small size, 

 with aquatic habit, and with relatively low zoological 

 rank. The young of a starfish, for example, has hardly 

 a character in common with its parent, while a marine 



1 The dates in brackets after authors' names will facilitate 

 reference to the Bibliography (pp. 124-8). 



