106 Darwin- Wallace Celebration. 



to the other. Domestic animals are abnormal, irregular,, 

 artificial ; they are subject to varieties which never occur 

 and never can occur in a state of nature : their very exist- 

 ence depends altogether on human care ; so far are many of 

 them removed from that just proportion of faculties, that 

 true balance of organization, by means of which alone an. 

 animal left to its own resources can preserve its existence and 

 continue its race. 



The hypothesis of Lamarck that progressive changes in< 

 species have been produced by the attempts of animals to 

 increase the development of their own organs, and thu& 

 modify their structure and habits has been repeatedly and 

 easily refuted by all writers on the subject of varieties and 

 species, and it seems to have been considered that when this 

 was done the whole question has been finally settled ; but the 

 view here developed renders such an hypothesis quite un- 

 necessary, by showing that similar results must be produced 

 by the action of principles constantly at work in nature. The 

 powerful retractile talons of the falcon- and the cat-tribes 

 have not been produced or increased by the volition of those 

 animals ; but among the different varieties which occurred 

 in the earlier and less highly organized forms of these 

 groups, those always survived longest wliicli had the greatest 

 facilities for seizing their prey. Neither did the giraffe acquire 

 its long neck by desiring to reach the foliage of the more- 

 lofty shrubs, and constantly stretching its neck for the 

 purpose, but because any varieties which occurred among its 

 antitypes with a longer neck than usual at once secured a 

 fresh range of pasture over the same ground as their shorter- 

 necked companions, and on the first scarcity of food were' 

 thereby enabled to outlive them. Even the peculiar colours of 

 many animals, especially insects, so closely resembling the 

 soil or the leaves or the trunks on which they habitually 

 reside, are explained on the same principle ; for though in 

 the course of ages varieties of many tints may have occurred,. 

 yet those races having colours lest adapted to concealment from 

 their enemies would inevitably survive the longest. We have 

 also here an acting cause to account for that balance so often 

 observed in nature, a deficiency in one set of organs always 

 being compensated by an increased development of some- 

 others powerful wings accompanying weak feet, or great 

 velocity making up for the absence of defensive weapons ; 

 for it has been shown that all varieties in which an un- 

 balanced deficiency occurred could not long continue their 

 existence. The action of this principle is exactly like that 



