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THE AMERICAN NATURALIST 



[Vol. LVI 



tein substance the motli makes carboliydrate, fat, and 

 water to supply the needs of its system. The bee moth 

 subsists on bee comb, which contains less than one per 

 cent, of protein and a large amount of rather insoluble 

 wax. Ants not only acquire food from the environment, 

 but give up what they have already swallowed to their 

 fellows, even when they are hungry themselves. In this 

 case the ''system" of the colony is more important than 

 that of the individual. 



In order to keep their systems of activities intact, ani- 

 mals have adopted many means to escape dangers. There 

 are lurking enemies, physical changes, accidents, insidi- 

 ous parasites to be met or avoided continually. A walk- 

 ing-stick spends nine-tenths of its life in a "perfectly 

 quiescent" state, depending on being overlooked by 

 hungry enemies. A house fly escapes through endless 

 agility. A rotifer avoids drying up by secreting a cyst 

 about itself, and may remain dormant for years. Many 

 animals are able to change the usual rate of their meta- 

 bolic activities in response to changes in temperature and 

 pass cold periods in a hibernating state. 



Animals, before all things, use the means they possess 

 in order to perpetuate their particular systems. New indi- 

 viduals must continually be started on new life cycles and 

 such recreations involve reorganizations of systems, 

 changes in metabolism, and various responses by organ- 

 isms to the environment. Such qualities as odors, colors, 

 and songs may be very important for the survival of a 

 race. A male moth will migrate a mile or more to find a 

 mate— attracted by her odor. The daily routine of seek- 

 ing and escaping dangers is often neglected by animals 

 when the survival of their race is concerned. Greedy 

 penguins allow any youngster that comes to feed from 

 their crops. An adult bull seal takes no food from May 

 to August, but devotes all his energies to the defense of 

 his rookery. The male gaff-tops '1 catfish takes the eggs 

 from his mate and carries them in his mouth for ninety 

 days— denying himself food in order that his offspring 



