BRITISH ASSOCIATION. 317 



flowers one which was partly red. By breeding he raised from this 

 a form wholly red. Evidently the yellow and the wholly red are the 

 pure forms, and the partially red is the heterozygote. We may then 

 say that the yellow is YY with two doses of a positive factor which 

 inhibits the development of pigment ; the red is yy, with no dose of 

 the inhibitor ; and the partially red are Yy, with only one dose of it. 

 But we might be tempted to think the red was a positive charac- 

 teristic, and invert the expressions, representing the red as BB, the 

 partly red as Br, and the yellow as rr. According as we adopt the 

 one or the other system of expression we shall interpret the evolu- 

 tionary change as one of loss or as one of 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 

 knowledge we can positively declare to be not due to loss. When 

 this has been conceded it is natural to ask whether the removal of in- 

 hibiting 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 encouragement 

 or sanction to the view that gradual evolution occurs by the trans- 

 formation of masses of individuals, though that fancy has fixed itself 



