166 THE THEORY OF EVOLUTION 



placement and recombination in full conformity 

 with established principles of heredity behavior." l 



These and many similar questions must be left 

 to future investigations for reply; it is, in any event, 

 a great advance that we should be able to approach 

 these problems by means of exact experiment and 

 mathematical analysis. 



This concludes our sketch of the various lines of 

 testimony which have been adduced in favour of 

 the theory of evolution and I can readily imagine 

 that some of you, at least, are saying to yourselves: 

 "Is that all? I don't think that amounts to much!" 

 For such lack of conviction, if such there be, there 

 are obvious reasons. It has been necessary, because 

 of the very brief time at our disposal, only six hours 

 all told, to make a very limited selection out of the 

 great mass of evidence that might otherwise have 

 been brought forward. However candidly and skil- 

 fully the selection may be made, it cannot produce 

 the same impression, as when the whole body of 

 testimony can be presented, a principle which is 

 well understood in the courts of justice. I have 

 said very little with regard to plants, picking out 

 only a few conspicuous examples, yet the evidence 

 in their case is the same as for animals, fuller and 

 clearer in some respects, less so in others. Professor 

 Giesenhagen sums up for plant evolution thus: "The 

 evidence disclosed by palaeontology shows us that 



1 Wm. Laurence Tower, in Heredity and Eugenics, Chicago, 1912, 

 pp. 222-3. 



