278 ANIMAL STUDIES 



robin are hatched and protected, and the helpless fledglings 

 are fed and cared for until able to cope with their natural 

 enemies. In the next year another brood is carefully reared, 

 and so on for the few years of the robin's life. 



Under normal conditions in any given locality the num- 

 ber of individuals of a certain species of animal remains 

 about the same. The fish which produces tens of thousands 

 of eggs and the bird which reproduces half a dozen eggs a 

 year maintain equally well their numbers. In one case a 

 few survive of many born ; in the other many (relatively) 

 survive of the few born ; in both cases the species is effect- 

 ively maintained. In general, no agency for the perpetua- 

 tion of the species is so effective as that of care for the 

 young. 



246. 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- 



