The Making of Species 



little room for doubt that it would be seized upon 

 and preserved by natural selection, whenever it 

 occurred. 



As E. H. Aitken very truly says, "so early 

 and useful an invention should, one would think, 

 have been spread widely in after time ; but 

 there appears to be some difficulty in developing 

 muscles at the thin end of a long tail, for the 

 animals that have turned it into a grasping organ 

 are few and are widely scattered. Examples 

 are the chameleon among lizards, our own little 

 harvest mouse, and, pre-eminent among all, the 

 American monkeys" (Strand Magazine, Nov. 

 1908). 



Even as there are many variations which seem 

 never to occur in nature, so are there others 

 which occur so frequently that they may be 

 looked for in any species. Albinistic forms 

 appear now and again hi almost every species 

 of mammal or bird ; while melanistic sports, 

 although not so common, are not by any means 

 rare. 



Every complete manual on poultry gives for 

 each breed a note of the faults which constantly 

 appear, and which the fancier has to watch care- 

 fully for and guard against. The fact that these 

 11 faults" occur so frequently in each breed shows 

 how strong is the tendency to vary in certain 

 definite directions. It is true that some of these 

 faults are in the nature of reversions, as, for 



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