OF ARTS AND SCIENCES. 429 



1. The intervention of man has produced, by careful and continued 

 selection, very remarkable changes in races both of domestic animals 

 and plants. 



2. Nature constantly produces varieties. Therefore, 



3. Nature, which commands indefinite periods of time, may, by seiz- 

 ing accidental varieties in which some peculiarity appears favorable to 

 the individual in the great struggle for life, so extend and improve this 

 peculiarity as gradually to evolve new and more gifted species. 



It was clear that he could not logically stop here, and he does not 

 shrink from the conclusion, that in like manner genera have been evolved 

 from species, orders from genera, and so on, until at last you come back 

 to one original pair, progenitors of all the visible animated creation. 



To this reasoning Mr. Lowell objected : — 



1. That man acts with means of seclusion that Nature does not 

 possess, and that accordingly varieties always tend to return to the origi- 

 nal type, instead of diverging from it. 



2. That the changes produced by human agency are all within spe- 

 cijic limits ; that is, that the operation consists in developing certain 

 observed tendencies, and discouraging others ; but that there is not the 

 slightest approach towards generic changes. The most improved South- 

 down ram, or Ayrshire bull, is but a ram or a bull after all. You can- 

 not, therefore, reason from this analogy, whatever time be assumed, to 

 any changes differing in kind from specific changes. 



3. The theory rests entirely on the second proposition, that Nature 

 is constantly producing varieties. Mr. Darwin must therefore be held 

 to strict proof of this. The existence of varieties in the animal king- 

 dom is denied by very high authority. As to the vegetable kingdom, 

 so long as botanists took it for granted that all hermaphrodite plants 

 were self-fertilized, every departure from the normal type was of course 

 a variety. But Mr. Darwin has shown by numerous instances that 

 fertilization is constantly occurring by the intervention of insects, who 

 transport to one flower the pollen of another, and that this occurs not 

 only between plants of the same species, but also between those of dif- 

 ferent species. He even doubts whether any species can be long main- 

 tained by self-fertilization alone. Such being the case, it becomes a 

 legitimate subject of inquiry whether all the so-called varieties are not 

 produced by hybridization. We know that, in crossing breeds, one off- 

 spring will resemble one parent, one the other, and others have a type 



