436 ANNALS NEW YORK ACADEMY OF SCIENCES 



This of course refers to discontinuous variations in organisms under 

 natural conditions, for he had certainly found evidence to make him believe 

 in similar variations among domesticated animals and plants. I think Mr. 

 Darwin never specified the directions in which a belief in mutation would 

 be a help to him, but, from casual remarks made in various places, I fancy 

 he had in mind the way in which it would ease liim over that difficult subject, 

 the imperfection of the geological record, and would reconcile him with the 

 physicists and cosmogonists, who were not disposed to allow him the lapse 

 of past time he required for the evolution of species by the accumulation of 

 successive minute or "insensible" individual variations. But I will not 

 discuss these points now. What I wish to dwell upon at the moment is 

 that Darwin recognized and accepted the fact of mutation among animals 

 and plants under domestication, although it is worth while to repeat the 

 statement that some of his cases probably happened in a state of nature, 

 since they occurred at the very beginning of, and were the points of origina- 

 tion for, man's selective operations. As Mr. Darwin himself says: "Man 

 can hardly select, or only with much difficulty, any deviation of structure 

 excepting such as is externally visible," ^ which means, as I take it, that 

 nature usually presents some quite manifest variation before artificial selec- 

 tion begins and this must have been the case at the time when man's first 

 choices were made, particularly when half-civilized and unobserving men 

 began the cultivation of our now domesticated animals and plants. It is 

 necessary to remember, however, in this connection, that the mutation 

 theory, as interpreted by de Vries, requires for its starting point only a varia- 

 tion which marks a distinct separation of a form from its parent group with- 

 out connecting gradations, and not necessarily any great or extraordinary 

 change of characters; for, as he says: "Species are derived from other 

 species by means of sudden small changes which, in some instances, may 

 be scarcely perceptible to the inexperienced eye." ^ None the less it remains 

 true that man is apt to select only striking variations and hence Mr. Darwin, 

 in treating of "sports," or what we should now call mutants, among culti- 

 vated plants and animals, usually speaks of them as wide departures from 

 type, or, rather, he deals only with such as are large deviations. Even when 

 treating of organisms in a state of nature, however, he admits that "there 

 will be a constant tendency in natural selection to preserve the most divergent 

 offspring of any one species." ^ Returning to the subject of artificial selec- 

 tion, Mr. Darwin says : 



> •' Origin of Species," 6th ed., p. 2S. 



2 " Plant Breeding," 1907, p. 9. 



3 " Origin of Species," 6th ed., 1882, p. 413. 



