18 COSMIC PHILOSOPHY. [pt. ii. 



would become so thoroughly altered as to constitute a distinct 

 species from their graceful, swift, and timid ancestors. It is 

 in just these ways that New Zealand birds, freed by insular 

 isolation from the attacks of mammalian enemies, have grown 

 lai'ge and clumsy, and have lost the power of flight which 

 their partly-aborted wings show that they once possessed. 



By the same kind of illustration we may form a rough 

 notion of the way in which a single species bifurcates into 

 two well-defined species. Suppose a race of ruminants to 

 have been living in Africa before the introduction of car- 

 uivora, and suppose that, for sundry reasons, the vitality of 

 the race was but little affected by moderate variations in 

 the sizes of its individuals, so that while some were com- 

 paratively light and nimble, others were comparatively large 

 and clumsy. Now introducing upon the scene the common 

 ancestor of the lion and the leopard — by immigration either 

 from Asia or from some other adjacent territory now sub- 

 merged — let us note some probable features of the complex 

 result. First, as regards the attacked ruminants, it is likely 

 that in course of time the lightest and swiftest individuals, 

 habitually taking refuge in flight, would have greatly increased 

 both in fleetness and in timidity ; the largest and most clumsy 

 of the species, unable to save themselves by fleeing, would 

 often be forced to stand and fight for their lives, and would 

 thus ultimately have gained in size, strength, and courage ; 

 while those who were neither nimble enough to get out of 

 the way nor strong enough to fight successfully would have 

 all been killed off. And thus, after a while, by perpetual 

 destruction of the means and preservation of the extremes, 

 we should get two kinds of ruminant as different from one 

 another as the antelope which escapes by his fleetness and 

 cauticus timidity, and the buffalo which boldly withstands 

 the lion and not unfrequently conquers or repulses him. 

 Secondly, let us observe what must have been going on all 

 the while with the attacking carnivora. The lighter and less 



