724 Mr. J. Lewis Bonhote : Subspecies [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 that nature proceeds on different 
lines from man because varieties produced by human agency 
easily revert, is fallacious if we compare the aeons during 
which natural selection has acted, compared with the com¬ 
paratively few generations during which artificial selection 
has been conducted. The fact, however, that variations 
artificially produced by man through an alteration of environ¬ 
ment have been inherited for several generations when normal 
conditions were resumed, has been proved by Mr. W. E. 
Agar on variations in a Cladoceran (Simocephalus vetulus), 
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 forms 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 appear, 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 sporadically. 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 
