VARIATIONS, DUE TO REVERSION. 85 



above mentioned, it is proven that an animal is not 

 capable of modification in any of its characters, with- 

 out proportional injury to its physiological integrity; 

 and that a distinct species may not be produced by 

 such a process of degeneration ; for, sterility and death 

 ensue, before half of the requisite amount of change, in 

 structure, can be effected. 



Speaking of the "similar characters," which "make 

 their appearance in the several varieties or races de- 

 scended from the same species," he says : 



"These facts are important from showing, as re- 

 marked in a former chapter, that each trifling varia- 

 tion is governed by law, and is determined, in a much 

 higher degree, by the nature of the organization, than 

 by the nature of the conditions to which the varying 

 being has been exposed." 



Darwin confesses, that, of this "law," and of "the 

 nature of the organization," he is wholly ignorant. As 

 he says, " Our knowledge of the cause of variation is 

 profound." For "law," and for "the nature of the 

 organization," read, the power of reversion of charac- 

 ters once lost by the given species; and the above 

 counters for ignorance may be eliminated from the 

 problem. 



Again he says (page 502, Vol. ii, Animals and 

 Plants, &c): 



"Although every variation is either directly or in- 

 directly caused by some change in the surrounding 

 conditions, we must never forget that the nature of the 

 organization which is acted on, essentially governs the 

 result. Distinct organisms, when placed under similar 

 8* 



