1464 THE STORY OF THE UNIVERSE 



during the earlier stages of life, and has been fitting 

 them for entering upon the final part of their exist- 

 ence, which may extend for a longer or shorter pe- 

 riod, but which is mainly devoted to the continuation 

 of the species. The time occupied in the develop- 

 ment of insects varies greatly in different groups. 

 Cold and damp appear to delay this process. The 

 chrysalis of a butterfly has been kept for two years in 

 an icehouse, without undergoing development; while 

 on removal to a warm place it became transformed 

 into the winged insect. The cockchafer occupies 

 three years in its development, the duration of life in 

 its perfect state being probably only a single year. 



STRUGGLE FOR EXIST- 

 ENCE. CHARLES DARWIN 



AMONG organic beings in a state of nature 

 there is some individual variability: indeed I 

 agi not aware that this has ever been disputed. It 

 is immaterial for us whether a multitude of doubtful 

 forms be called species or sub-species or varieties; 

 what rank, for instance, the two or three hundred 

 doubtful forms of British plants are entitled to hold, 

 if the existence of any well-marked varieties be ad- 

 mitted. But the mere existence of individual 

 variability and of some few well-marked varieties, 

 though necessary as the foundation for the work, 

 helps us but little in understanding how species arise 

 in nature. How have all those exquisite adaptations 

 of one part of the organization to another part, and 

 to the conditions of life, and of one organic being to 



