20 PRESIDENT’S ADDRESS. 
addition. May we not interpret the other apparent new dominants in 
the same way? The white dominant in the fowl or in the Chinese 
Primula can inhibit colour. But may it not be that the original coloured 
fowl or Primula had two doses of a factor which inhibited this inhibitor ? 
The Pepper Moth, Amphidasys betularia, produced in England about 
1840 a black variety, then a novelty, now common in certain areas, 
which behaves as a full dominant. The pure blacks are no blacker 
than the cross-bred. Though at first sight it seems that the black 
must have been something added, we can without absurdity suggest 
that the normal is the term in which two doses of inhibitor are present, 
and that in the absence of one of them the black appears. 
In spite of seeming perversity, therefore, we have to admit that 
there is no evolutionary change which in the present state of our know- 
ledge we can positively declare to be not due to loss. When this has 
been conceded it is natural to ask whether the removal of inhibiting 
factors may not be invoked in alleviation of the necessity which has 
driven students of the domestic breeds to refer their diversities to 
multiple origins. | Something, no doubt, is to be hoped for in that 
direction, but not until much better and more extensive knowledge of 
what variation by loss may effect in the living body can we have any real 
assurance that this difficulty has been obviated. We should be greatly 
helped by some indication as to whether the origin of life has been single 
or multiple. Modern opinion is, perhaps, inclining to the multiple 
theory, but we have no real evidence. Indeed, the problem still stands 
outside the range of scientific investigation, and when we hear the 
spontaneous formation of formaldehyde mentioned as a possible first 
step in the origin of life, we think of Harry Lauder in the character of 
a Glasgow schoolboy pulling out his treasures from his pocket—‘ That’s 
a wassher—for makkin’ motor cars *! 
As the evidence stands at present all that can be safely added in 
amplification of the evolutionary creed may be summed up in the 
statement that variation occurs as a definite event often producing a 
sensibly discontinuous result; that the succession of varieties comes 
to pass by the elevation and establishment of sporadic groups of 
individuals owing their origin to such isolated events; and that 
the change which we see as a nascent variation is often, perhaps 
always, one of loss. Modern research lends not the smallest encourage- 
ment or sanction to the view that gradual evolution occurs by the trans- 
formation of masses of individuals, though that fancy has fixed itself on 
popular imagination. The isolated events to which variation is due are 
evidently changes in the germinal tissues, probably in the manner in 
which they divide. It is likely that the occurrence of these variations 
is wholly irregular, and as to their causation we are absolutely without 
surmise or even plausible speculation. Distinct types once arisen, no 
