12 ORGANIC EVOLUTION— PHYSICAL 



spondingly slow. To take an example — a buck and 

 a doe antelope, whose sight and hearing respectively 

 are keener than the average, but whose other qualities 

 are equal to the mean of the species, are at an advantage 

 as regards the sense of sight and hearing respectively. 

 If they mate, the offspring, while attaining to the specific 

 mean in the other qualities, will in general surpass it 

 as regards sight and hearing, but will fall below the 

 male parent as regards the sight, and the female 

 parent as regards the hearing; for the comparative 

 dullness of the male's hearing will militate in the 

 offspring against the keenness of the female's hearing, 

 and vice versd as regards the sight. So also with the 

 offspring of a buck pre-eminent for endurance and a 

 doe pre-eminent for speed. Then, if the offspring of 

 the two pairs mate, their offspring will surpass, but 

 in a lessening degree, the specific mean in keenness 

 of sight and hearing, in speed and in endurance, but 

 will fall below each of the grandparents as regards 

 the one quality in which that grandparent excelled, 

 though they will surpass each of them as regards all 

 the other qualities. Therefore if the essential quali- 

 ties are numerous, — and they always are so in the case 

 of wild animals, — the descendants of numerous ancestors, 

 each one of whom was pre-eminent in one of these 

 qualities, will tend more and more, generation after 

 generation, to approach the general racial mean as 

 regards all these qualities ; — which appears to lead to 

 the absurd conclusion, that in the end there will be no 

 evolution at all. But in coming to that conclusion we 

 shall have forgotten that the offspring never present an 

 exact mixture of the qualities of the parents, but that 

 spontaneous variations, caused we know not how, con- 

 tinually arise, in consequence of which one or more of 

 the offspring of the keen-sighted father and the quick- 

 hearing mother (for instance) may surpass both parents 



