PRESIDENTIAL ADDRESS. 233 



among all other possible variations — variations which were 

 not only possible, but which actually occurred, only elimina- 

 tion swept them away. 



Does the evidence afforded by fossil remains help us 

 here ? Those American zoologists who have studied the 

 evolution of mammalian teeth contend that the occurrence 

 of new points and cusps is not indeterminate bnt deter- 

 minate. New elements of tooth-structure appear in, definite 

 positions. There is nothing to indicate selection from among 

 indefinite variations. Other evidence of like implicatian 

 is adduced by American evolutionists ; but this of tooth- 

 structure is put forward as the strongest case. I am in- 

 clined to think that the facts of palseontology, so far as 

 they go, point in this direction. But I question whether 

 they can be regarded as conclusive. In criticising the 

 position stress may be laid on the imperfection of the 

 geological record ; and it may be urged that the number of 

 individuals in our palaeontological collections is not sufficient 

 to constitute a truly representative sample. Furthermore, 

 on the hypothesis of selection, the individuals possessed of 

 teeth with points and cusps in other than these adaptive 

 positions must have been weeded out in the early stages 

 of life. In view of these objections the evidence cannot be 

 said to be convincing, though in my opinion it affords some 

 presumption in favour of determinate variation. 



Some direct evidence in this matter might be obtained' 

 by a careful, extensive, and long-continued series of obser-- 

 vations on fish, amphibians, and insects, by rearing and' 

 examining all the individuals hatched out from a considerable 

 number of batches of ova. It would not be sufficient to 

 examine merely the numerous progeny of a single individual, 

 since they would be likely to present in excess particular 

 inherited tendencies. But if such determinate variations 



