August 28, 1914] 



SCIENCE 



301 



inhibitor are present, and that in the ab- 

 sence of one of them the black appears. 



In spite of seeming perversity, therefore, 

 we have to admit that there is no evolution- 

 ary change Avhich 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 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. Modem opinion is, perhaps, 

 inclining to the multiple theory, but we 

 have no real evidence. Indeed, the problem 

 still stands outside the range of scientific in- 

 vestigation, and when we hear the spon- 

 taneous formation of formaldehyde men- 

 tioned 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 indi- 

 viduals 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 



transformation 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 oc- 

 currence of these variations is wholly ir- 

 regular, and as to their causation we are 

 absolutely without surmise or even plaus- 

 ible speculation. Distinct types once 

 arisen, no doubt a profusion of the forms 

 called species have been derived from them 

 by simple crossing and subsequent recombi- 

 nation. New species may be now in course 

 of creation by this means, but the limits of 

 the process are obviously narrow. On the 

 other hand, we see no changes in progress 

 around us in the contemporary world 

 which we can imagine likely to culminate in 

 the evolution of forms distinct in the larger 

 sense. By intercrossing dogs, jackals and 

 wolves, new forms of these types can be 

 made, some of which may be species, but I 

 see no reason to think that from such ma- 

 terial a fox could be bred in indefinite time, 

 or that dogs could be bred from foxes. 



Whether science will hereafter discover 

 that certain groups can by peculiarities in 

 their genetic physiology be declared to have 

 a prerogative quality justifying their recog- 

 nition as species in the old sense, and that 

 the differences of others are of such a sub- 

 ordinate degree that they may in contrast 

 be termed varieties, further genetic re- 

 search alone can show. I myself anticipate 

 that such a discovery will be made, but I 

 can not defend the opinion with positive 

 conviction. 



Somewhat reluctantly, and rather from a 

 sense of duty, I have devoted most of this 

 address to the evolutionary aspects of ge- 

 netic research. We can not keep these 

 things out of our heads, though sometimes 

 we wish we could. The outcome, as you will 

 have seen, is negative, destroying much that 



