346 Letters , Extracts, and Notes . [Ibis, 
sceptical on the point as to whether Natural Selection, 
acting on even discontinuous variations, can have any 
practical effect on the formation of species, or whether 
it is not superfluous to invoke the action of Natural 
Selection at all—nor do we believe in the action of en¬ 
vironment in the initiation of new species. The only thing 
in our opinion which can give rise to a new species is the 
conjugation of two gametes possessed of some unusual 
factor or other to form a zygote. We believe that the 
beginnings of a new species may occur from the union 
of any two birds anywhere, and is a matter of the chance 
presence or absence, stimulation or suppression, of factors 
in the germ-plasm. It must be remembered, however, that 
over so small a part of the world’s history do man’s obser¬ 
vations extend in point of time, that we cannot definitely 
state whether or not species are being formed at all at the 
present day. 
There is, moreover, a point in this question of the value 
of subspecies to which we cannot help thinking ornitholo¬ 
gists in general have not hitherto paid sufficient attention. 
They appear, indeed, to have ignored the very probable fact 
that there are two main forms of variations—one known as 
u mutational,” in which the variation is discontinuous and 
dependent on the presence in the organism of definite 
factors which are resident in the germ-plasm , and which are 
therefore heritable , the other known as a “ fluctuational,” 
“ environmental,” or continuous variation, which is directly 
due to the action of the environment on the soma during 
the lifetime of the organism, and which effect cannot be 
passed on to future generations. 
We think there can be little doubt that many—indeed, by 
far the majority—of our present-day subspecific forms belong 
to this last category, and are mere environmental, unstable, 
and essentially superficial variations, which would quickly 
disappear if the organism were transferred from its normal 
environment to some other of a different nature. Many 
such environmental subspecies present variations which are 
