20 DARWIN'S THEORY. 



Darwin, availing himself thus of the presumption of 

 no-limit (which, other things legitimate would be itself 

 legitimate) takes the fact, that, during a short period 

 under domestication, most numerous and important 

 improvements have sprung up, in animals and plants ; 

 and he concludes therefrom, that the species are not 

 immutable ; that varieties are but incipient species ; 

 that each and every species changes, with the changes 

 in the individuals of which it is composed ; and that, 

 given a sufficient length of time — he intimates several 

 millions of generations — it is quite probable, that, at 

 the same (or even greatly less) rate of improvement 

 now displayed under our very eyes, the higher forms 

 will go on progressing, and improving, into still higher 

 forms ; and that the lower forms will develop into the 

 higher forms : And that, as these changes of structure, 

 occurring now with each individual, are accumulated, 

 and made to form divergent varieties within each spe- 

 cies ; each variety of such species will further di- 

 verge into species, distinct from the parent species ; 

 and evolve, also, into other genera, families and 

 orders. 



In other words, he concludes, from the progress 

 made with domesticated animals, that a variety of the 

 Duck species, for example, will diverge into several 

 distinct types, as high in the order of beings, as the 

 Fowl, the Goose, the Turkey,. the Peacock, the Con- 

 dor, and the Eagle ; and, that, there would be nothing 

 impossible, but rather probable, in the circumstance of, 

 another variety of the Duck diverging, successively, 

 into the Bat, the Flying-Squirrel, the Rabbit, the Pig, 



