GROUNDS AND CONSEQUENCES OF EVOLUTION. 335 



that no ground whatever remains for the old assumption 

 that each species is a separate creation. It is certainly 

 safe, on the grounds of natural evidence, and, as I will 

 attempt to show in the sequel, on the ground of religion, 

 to admit that family resemblances among animals, as 

 among mankind, imply community of descent. 



This principle achieved, very much is found involved 

 in it. Resemblances of the same nature as those called 

 family resemblances exist between groups of animals and 

 plants quite widely differentiated from each other. We 

 do not say the mouse and the rhinoceros possess a family 

 resemblance, but it is demonstrable that they do possess 

 profound resemblances aggregating vastly more than all 

 their differences. Their differences relate to size, cover- 

 ing, habits and other trivial circumstances; while their 

 resemblances include skeletal frame-work, circulatory, di- 

 gestive, respiratory and reproductive organization, as well 

 as the general plan, arrangement, juxtaposition, connec-. 

 tion and coaction of these systems, and all the minuter 

 plan, substance, structure, development and action of 

 bone, nerves, skin, fibres, membranes, etc. Finally, both 

 have warm blood, respire air, and nourish their young 

 with milk. How can we escape the conviction that these 

 animals, also, owe their amazing similarity of constitution 

 to their common descent from some remote ancestor? 



But, if we compare the ox and the alligator, and free 

 our minds from the customary impression made by their 

 external contrasts, we shall find that almost the same 

 identical catalogue of resemblances must be made out. 

 The alligator is. cold-blooded (comparatively), and does 

 not nourish its young with milk. Its circulation is not 

 completely double, though the rudiments of the same cir- 



