DARWIN'S THEORY. 33 



slight successive, positive variation, there has been a 

 prodigious amount of degeneration, during the past, 

 under nature. Natural Selection has very frequently 

 simplified and degraded the structure of animals and 

 plants. 



So widespread, Darwin says, has been this degenera- 

 tion, under nature, that there exists now scarcely a 

 single species which has not lost some organs or 

 features. 



From changed habits of life, and from the hard 

 conditions of the Struggle for Existence — which needs 

 must be excessively vigorous to give play to Natural 

 Selection — organs, he says, have become of less and 

 less use, and ultimately superfluous; and disuse, and 

 Natural Extinction, acting on the individuals, have 

 gone on reducing the organs, until, finally, they have 

 either become wholly suppressed, leaving not a vestige 

 of their existence (save the power of reappearing 

 which, he says, they are ever competent to do, even 

 after having lain latent for millions of generations); 

 or, they have become only greatly reduced, having the 

 character of rudiments. 



With respect to this power of Reversion, in the 

 many long-lost characters ; he says, that characters, 

 proper to both sexes, to both the right and left side of 

 the body, and to a long line of male and female ances- 

 tors, separated by hundreds, or even thousands of gen- 

 erations from the present time, frequently lie latent in 

 many individuals, without our being able to detect any 

 signs of their presence; yet that "these characters, 

 like those written on paper with invisible ink, all lie" 



