438 THE RESULTS OF EVOLUTION 



concerned in this matter of rivalry. Among certain of 

 the fishes, such as the sahnon, trout, and stickleback, 

 there are combats ranging from sudden rushes, without 

 any material damage resulting, to bitterly contested 

 struggles where death may result, teeth being the organs 

 chiefly concerned. Many of the turtles, lizards, and croco- 

 diles also engage in lively tilts during the breeding season, 

 using teeth, claws, or beaks as weapons. Among the birds 

 there are many species, chiefly those related to the 

 pheasants and domestic fowl, where spurs and wings and 

 beaks are at times used with deadly effect. Among the 

 higher animals, especially those where one male strives 

 to gain possession of several females, the struggles are 

 even more severe. This is especially true of certain 

 species of wild sheep and swine and of some of the deer 

 and antelope tribe, where teeth and hoofs lay the van- 

 quished low or drive him from the field. 



Rivalry among Plants. — If anyone is in doubt as to 

 the existence of rivalry among plants let him repeat the 

 experiment of Darwin, in which a small plot of ground 

 was cleared and a census taken of the large number of 

 individual plants which germinated and of the small 

 number which came to maturity. As in the case of ani- 

 mals the struggle for supremacy is most severe among the 

 members of the same species, so that throughout its range 

 many more individuals are born than are able to live and 

 reproduce. But while it is true that only a limited num- 

 ber of offspring of a single species can live in one locality, 

 this does not prevent members of other species from flour- 

 ishing in the same region. A glance at the vegetation of 

 any field or forest is sufficient to prove this fact. In 

 either event, however, whether the rivalry is between the 

 individuals of the same or different species, the ill-adapted 

 die in the struggle. Just what a<:laptations are the most 

 valuable aids in achieving success is difficult to decide. 

 Obviously, a favorable location is of prime importance, 

 and a vigorous constitution is scarcely less so. It is also 



