4 CHAPTERS ON EVOLUTION. 



ancients, and as we no longer utilise their geology as serviceable 

 or true, we can afford to dispense with their biological views, 

 and we therefore turn hopefully to the second and scientific concep- 

 tion of the origin of living beings. This conception is the theory 

 of " Derivation," " Descent," or ' Evolution." 



According to the evolutionist, the universe of life, instead of 

 being composed of a series of fixed and unchangeable units 

 unvarying as when they were first " created " on the former theory 

 of life's origin is the theatre of incessant variation and change. 

 Each " species " or " kind " of animals and plants, instead of existing 

 as a stable unvarying group, as the older naturalists defined it, is seen 

 to vary to a greater or less degree, according to internal and con- 

 stitutional, or to external conditions, or under the influence of both 

 combined. The progeny do not rigidly resemble the parents, but 

 continually exhibit differences in colour, size, and other peculiarities. 

 Thus " variations " in species are produced ; and these variations 

 may appear of singularly wide character when conditions favouring 

 change have operated in their production. In this way the existing 

 " species " are modified, and the new " varieties " thus produced, in 

 time give origin to new species. These latter are, therefore, viewed 

 as having been " evolved " by natural descent, that is by the ordinary 

 laws of generation and reproduction, from the older species. The 

 animal and plant worlds regarded in this light are liable to 

 perpetual modification, and the experience of every-day life seen 

 familiarly in the culture of plants, and in the breeding of horses, 

 cattle, sheep, dogs, and pigeons amply testifies to the mobility and 

 plasticity of the animal and plant constitutions. That is to say, man, 

 in the process of breeding animals, and by selecting the parents of 

 his domestic races, can " evolve " animals which, in time, differ from 

 the original stock far more widely than ordinary and so-called 

 " species " differ from one another. 



But the plasticity of " species " is far from being the only prop 

 and support of the theory of evolution. When the naturalist 

 attempts to classify animals or plants, he discovers that instead of 

 exhibiting each a specific and individualised structure, as might be 

 presumed were the " special creation " theory true, the various 

 groups of animals are linked together in such a fashion as to suggest 

 the existence of some natural bond of relationship between them. 

 With the plant world the case is analogous. The tribes of plants 

 are harmoniously connected together in such a manner as to 

 indicate a relationship which, as in the case of the animals, is only 

 satisfactorily explained on the idea of connected descent. What 

 explanation, for example, satisfying to the rational mind, can be 

 given of such a striking feature as that illustrated in the literally 

 marvellous correspondence which exists between the fore and hind 



