128 DISCRIMINATIONS CHAP. 



doctrine that changes in animal structure 

 can only have been very minute and very 

 slow. He, therefore, takes up the same 

 idea that has often occurred to me that 

 all the phenomena, even of ordinary 

 generation, point to the possibility of 

 great transmutations having been accom- 

 plished in very short periods of time. 

 It seems he had foreshadowed this line 

 of argument in 1852, before Darwin's 

 book was published. But he now works 

 it out in more detail, and revels in the 

 calculations which prove what great 

 things are now being very summarily 

 done by ordinary generation in develop- 

 ing the most complex organic forms 

 from a simple cell. The nine months 

 which are enough to develop the human 

 ovum into the very complex structure of 

 a new-born infant are divisible, he calcu- 

 lates, into 403,200 minutes. If only one 

 hundred millions of years were allowed 



