ON THE ORIGIN OF DEATH. 12$ 



nothing but the germ-cell of the Metazoa possesses this 

 immortality and vast power of reproduction. 



But to return to Weismann's views. If death is not 

 something which is inherent in living matter, but which 

 is acquired, how is it that the length of life differs so 

 markedly in different species } Weismann answers that 

 the age which an animal may attain has been deter- 

 mined by natural selection, and also that the power 

 of reproduction and length of life are correlated. In 

 order to understand this view it is necessary to compare 

 the length of life and reproductive powers of different 

 animals. Birds, as a rule, live to a surprisingly great age. 

 Even the smallest singing-birds live for ten years, while 

 some live for twelve or even eighteen years. A par- 

 tridge lives from twenty to twenty-five years. A pair 

 of eider-ducks were observed nesting in the same place 

 for twenty years, and it is believed that these birds 

 often reach the age of a hundred. The same cuckoo 

 was recognized by its peculiar note in the same forest 

 for thirty-two consecutive years. Birds of prey become 

 much older, for they outlive more than one generation 

 of men. A white-headed vulture was kept in a zoological 

 garden in Germany for one hundred and eighteen years ; 

 and many examples of eagles and falcons reaching an 

 age of over a hundred years have been recorded. Hum- 

 bolt mentions a parrot from the Orinoco, of which the 

 Indians told that none could understand it, for it spoke 

 the language of an extinct race. 



Now let us compare the length of life and reproduc- 

 tive powers of the partridge and an eagle, and see if 

 there is any reason why one should live longer than 

 the other. The partridge Uves a little more than twenty 



