724 Mr. J. Lewis Bonlioto ; Suhspecies [Ibis, 



constant selection by one breeder, under the same conditions, 

 is able to be carried out — say 25 to 50 generations at the 

 most; and what is that compared with the ages which it has 

 taken to develop species, or even subspecies ? Facts on this 

 subject being almost impossible to get, it is well to bear in 

 mind a paper by Mr. H. Lyster Jameson (Journ. Linn. Soc, 

 Zool. vol. xxvi. pp. 365-473) on a variety of a House-Mouse 

 on a sand-bank in Dublin Bay, which sand-bank has only 

 been in existence about 100 years ; in this case the dif- 

 ferentiation was only beginning and many normal coloured 

 mice were found. In short, the question of time is all 

 important, and to argue tliat nature proceeds on ditt'erent 

 lines from man because varieties produced by hiunan agency 

 Ciisily revert, is fallacious if we compare the icons during 

 which natural selection has acted, coni])ared with the com- 

 paratively few generations during which artiricial selection 

 has been conducted. The fact, however, that variations 

 artificially produced by man through an alteration of environ- 

 ment have been inheiited for several genei'ations when normal 

 conditions were resumed, has been proved by Mr. W. E. 

 Agar on variations in a Cladoceran {SimocepJialus vetuius), 

 and by Messrs. Delcourt & Guyenot on Drosophila (Proc. IV. 

 Int. Congr. Genetics, Paris, 1913, p. 478) ; so that we have 

 here considerable evidence that man's methods in producing 

 new forn)s are not fundamentally different from those 

 obtaining in nature. 



Colonel Meinertzhagen wonders that no artificial variety 

 of Fowl, Pigeon, or Canary has ever occurred in a wild 

 state. This statement, if correct, would not be unexpected, 

 since an artificial environment cannot occur in nature, and 

 if such varieties did a})pear, they would show themselves in 

 an initial stage and soon be swamped, whereas man has 

 developed and intensified them by selection. In a wider 

 sense, however, they do occur sporatlically. For instance, 

 a Canary — typically a green bird — is yellow in confinement, 

 yet the nearly allied Serin shows a considerable tendency to 

 yellow, and among Parrots (green birds) yellow varieties are 



