122 CHAPTERS ON EVOLUTION. 



Turning to the other side of the question, all that is mysterious 

 and inexplicable on the special-creation hypothesis, becomes clear 

 enough on that of " development " and " modification." By the idea 

 of development is implied the derivation of the similar forms, or 

 parts, from some common type, through natural laws of heritage and 

 descent. By " modification," or " adaptation," we mean to indicate 

 that potent power or factor, which, seizing the common type, moulds 

 the structure limb or body to the special way of life in which the 

 being ultimately comes to walk. 



If the latter idea be correct or feasible, we can readily assign a 

 reason why limbs, or any other series of structures in a given set of 

 animals, should present such a close likeness. " Conformity to 

 type " is no meaningless expression when used by the evolutionist. 

 By his theory, he views this conformity as a proof of the blood- 

 relationship far or near, as the case may be of the animals 

 which exhibit the likeness in question. Such similarity is a proof of 

 affinity, which can only be accounted for, in all its bearings, on the 

 supposition that the beings exhibiting it are really kith and kin, but 

 of varying degrees of relationship. It can readily be understood 

 how important in the eyes of the modern naturalist this study of 

 likenesses has become, since the facts it reveals largely assist him 

 in constructing the true pedigree of the living world. There are 

 many other considerations which serve to show the important nature 

 of such a branch of inquiry an importance equalled only by the 

 interest which its pursuit is certain to evoke. When, for instance, it 

 can be found that two organs so utterly unlike as the air-bladder of 

 a fish and the lungs of a man are in reality closely connected in 

 their nature, the information which the study of likenesses places at 

 our disposal is seen to be of a kind which tends very materially to 

 extend the knowledge that Bacon declared aided " the relief of man's 

 estate." And the task of seeking and finding resemblances has had 

 its due effect in solving not a few of the puzzles of biology. Only 

 from the considerations it brings to view, and through the influence 

 of the new way in which it compels us to regard forms and organs, 

 has the mystery of such a subject as that of "rudimentary organs " 

 been dispelled. The splint-bones of a horse, when examined by 

 the light of this study, guide us, as we have seen, to the history of 

 the equine race ; and the transformations of animals and plants 

 teem with new interest when investigated on the principles which 

 the science of likenesses brings to view. It is to the details of such 

 a subject that we now invite attention. Our illustrations will be 

 culled from both worlds of life ; and in our search after the likenesses 

 whereon hangs the past-history of the living being, we may per- 

 chance light upon considerations not far removed from the wider 

 questions that border the origin of man himself. 



