THE LIFE CYCLE 103 



large animals are long-lived and small animals have short 

 lives. 



61. Death. At the end comes death. After the animal 

 has completed its life cycle, after it has done its share toward 

 insuring the perpetuation of its species, it dies. It may 

 meet a violent death, may be killed by accident or by. ene- 

 mies, before the life cycle is completed. And this is the 

 fate of the vast majority of animals which are born or 

 hatched. Or death may come before the time for birth or 

 hatching. Of the millions of eggs laid by a fish, each egg 

 a new fish in simplest stage of development, how many or 

 rather how few come to maturity, how few complete the 

 cycle of life ! 



Of death we know the essential meaning. Life ceases 

 and can never be renewed in the body of the dead animal. 

 It is important that we include the words " can never be 

 renewed," for to say simply that " life ceases," that is, that 

 the performance of the life processes or functions ceases, 

 is not really death. It is easy to distinguish in most cases 

 between life and death, between a live animal and a dead 

 one, yet there are cases of apparent death or a semblance of 

 death which are very puzzling. The test of life is usually 

 taken to be the performance of life functions, the assimila- 

 tion of food and excretion of waste, the breathing in of oxy- 

 gen, and breathing out of carbonic-acid gas, movement, 

 feeling, etc. But some animals can actually suspend all 

 of these functions, or at least reduce them to such a mini- 

 mum that they can not be perceived by the strictest exami- 

 nation, and yet not be dead. That is, they can renew 

 again the performance of the life processes. Bears and 

 some other animals, among them many insects, spend the 

 winter in a state of death-like sleep. Perhaps it is but sleep ; 

 and yet hibernating insects can be frozen solid and remain 

 frozen for weeks and months, and still retain the power of 

 actively living again in the following spring. Even more 

 remarkable is the case of certain minute animals called Ro- 



