90 THE FOUNDATIONS OF ZOOLOGY 



old, and a-weary of their lives they hasten to the end. How differ- 

 ent the males when they make themselves up for intercourse, and 

 swelling with desire are excited by the venereal impulse ! It is 

 surprising to see with what passion they are inflamed, and then how 

 pugnacious they prove. But the grand business of life accomplished, 

 how suddenly and with failing strength, and pristine fervor quenched, 

 do they take in their swelling sails, and from late pugnacity grow 

 timid and desponding. Even during the season of jocund masking 

 in Venus's domains, male animals in general are depressed by inter- 

 course, and become submissive and pusillanimous, as if reminded 

 that in imparting life to others they were contributing to their own 

 destruction. The cock alone, replete with spirit and fecundity, still 

 shows himself alert and gay, clapping his wings and crowing tri- 

 umphantly, he sings the nuptial song at each of his espousals ; yet 

 even he, after some length of time in Venus's service, begins to fail; 

 like the veteran soldier, he by and by craves discharge from active 

 duty, and the hen, too, like the tree that is past bearing, becomes 

 effete, and is finally exhausted." 



Usefulness to one's kind is not entirely a matter of physiology. 

 The wisdom and cunning which long years of conflict with the ways 

 of the world have given to the old wolf is useful to the pack, even 

 after his bodily powers begin to fail, but all must agree with Harvey 

 that, with the loss of all usefulness or value to others, the final 

 end of the existence of the individual, so far as this is recognized 

 in nature, has been accomplished. 



While the law that the adaptations of nature serve to promote 

 the welfare of the species, rather than the good of the individual, 

 is as universal as life, it is usually hidden from view because the 

 welfare of the species is, in most circumstances, practically the 

 same as that of the individuals which compose it in each genera- 

 tion, and it is only when the two come into conflict, that the 

 law becomes manifest. When the welfare of the species demands 

 the sacrifice of individuals, the adaptations for securing this use- 

 ful end are as wonderfully perfect and efficient, and as obvious, 

 as any in nature. Most of them, like the self-sacrificing devotion 

 of the maternal instinct, relate to reproduction, and are so well 

 known that illustrations drawn from other fields may be more 

 novel, and therefore more impressive. 



