THEORY OF EXTRAORDINARY BIRTHS. 255 



The chief objection to Nageli's theory is, how- 

 ever, that the theory is more difficult to understand 

 than the facts which it attempts to explain. When 

 we attempt to imagine to ourselves what is meant 

 by an innate tendency, or how organisms can possess 

 it, we see at once that the theory is of no value 

 toward helping to an understanding of the problem. 

 The statement that organisms have an innate ten- 

 dency toward progression is simply another way of 

 saying that they have advanced, and are still advanc- 

 ing, toward greater complication. Nageli recognized 

 that organisms were advancing, saw that natural 

 selection was not sufficient for an explanation, and, 

 to comprehend the facts, assumes this tendency, of 

 which he knows nothing and can know nothing. 

 At best, therefore, it gives no better understanding 

 of evolution. It is of no assistance to say that this 

 tendency was placed in animals by the Creator, 

 until we can get some idea of what the tendency is 

 and how it can be transmitted from generation to 

 generation. While we may admit that such a ten- 

 dency, if it existed, would explain many difficult 

 problems, we must realize that there is no good 

 evidence for its existence, and that its very mean- 

 ing is obscure. To attempt to explain species on 

 such a theory is to abandon the attempt altogether, 

 and to admit the problem to be insoluble. 



Theory of Extraordinary Births. 



Somewhat akin to this idea of Nageli's, is the 

 theory of St. George Mivart. Similar, because in 

 like manner it appeals to internal causes acting on 



