20 POPULAR SCIENCE MONTHLY. 



animals. The two are so much opposed to each other in every circum- 

 stance of their existence, that what applies to the one is almost sure 

 not to apply 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 existence depends altogether 

 on human care; so far are many of them removed from that just pro- 

 portion of faculties, that true balance of organization, by means of 

 which alone an animal left to its own resources can preserve its exist- 

 ence and continue its race. 



The hypothesis of Lamarck — that progressive changes in species 

 have been produced by the attempts of animals to increase the develop- 

 ment of their own organs, and thus 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 unnecessary, by show- 

 ing 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 form of these groups, 

 those always survived longest which had the greatest facilities for seiz- 

 ing their prey. Neither did the giraffe acquire its long neck by desir- 

 ing 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 anti-types with a longer neck than usual at once 

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

 necTced companions, and on the first scarcity of food were thereby en- 

 abled 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 best adapted to conceal- 

 ment 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 unbalanced deficiency occurred could not long continue 

 their existence. The action of this principle is exactly like that of the 

 centrifugal governor of the steam engine, which checks and corrects 

 any irregularities almost before they become evident; and in like 

 manner no unbalanced deficiency in the animal kingdom can ever reach 



