44 PROGRESS OF PALEONTOLOGY n 



which they have endeavoured to connect as many 

 of these facts as they happened to be acquainted 

 .with. I do not think it would be a profitable 

 employment of our time to discuss conceptions 

 which doubtless have had their justification and 

 even their use, but which are now obviously incom- 

 patible with the well-ascertained truths of palae- 

 ontology. At present these truths leave room for 

 only two hypotheses. The first is that, in the course 

 of the history of the earth, innumerable species of 

 animals and plants have come into existence, in- 

 dependently of one another, innumerable times. 

 This, of course, implies either that spontaneous 

 generation on the most astounding scale, and of 

 animals such as horses and elephants, has been 

 going on, as a natural process, through all the time 

 recorded by the fossiliferous rocks ; or it necessitates 

 the belief in innumerable acts of creation repeated 

 innumerable times. The other hypothesis is, that 

 the successive species of animals and plants have 

 arisen, the later by the gradual modification of the 

 earlier. This is the hypothesis of evolution ; and 

 the palseontological discoveries of the last decade 

 are so completely in accordance with the require- 

 ments of this hypothesis that, if it had not existed, 

 the palaeontologist would have had to invent it. 



I hj^e always had a certain horror of presuming 

 to set a limit upon the possibilities of things. 

 Therefore I will not venture to say that it is im- 

 possible that the multitudinous species of animals 



