28 THE President's address. 



himself a biologist, for his work is barren and soulless. The 

 true systematist, on the other hand, is just as much inspired 

 with the enthusiasm of research and the thirst for knowledge as 

 the experimental biologist. The difference between the two 

 lies in the fact that the experimental biologist confines his 

 attention to the solution of certain fixed and definite problems 

 suggested by his own very limited knowledge of the organic 

 world, while the systematist studies the results of the infinitely 

 varied experiments which Nature has been performing upon 

 living organisms ever since they first appeared upon our planet. 

 The experimenter has undoubtedly the advantage of limiting 

 his problems so that they become more or less manageable and 

 of performing his experiments under more or less accurately 

 known conditions, but, on the other hand, there are many 

 problems with which he cannot deal at all and the solution of 

 which is no whit less important than that of the problems to 

 which he is obliged to restrict himself. Evolution is slow, but 

 human life is short, and slow changes may well be taking place 

 which we have no means of detecting by means of experiment or 

 direct observation. 



Professor Sollas has estimated the time actually occupied in the 

 evolution of the modern horse from its remote ancestor Eohippus 

 at some five or six millions of years. During this period the horse 

 has increased in height by 53 inches, or, allowing five years for 

 each generation, at an average rate of 0*00005 inch per genera- 

 tion. This is a rate of change which, supposing it to have taken 

 place gradually and not by a series of jumps, we could not hope 

 to detect by direct observation of living horses, especially when 

 we remember the fluctuations which must be occurring all the 

 while. Nevertheless it has led to extremely important results 

 in the course of time. The experimenter, again, could hardly 

 hope to observe the transitions by which a normal limb-bearing 

 lizard might pass into a limbless form such as the blind-worm. 

 The systematist, however, knows that in both cases intermediate 

 forms occur and is quite satisfied that, whether gradually or 

 otherwise, the transitions have actually taken place. 



There are, in short, many evolutionary problems which the 

 e:sq)erimentalist cannot touch but which t*he systematist may 



