410 STERILITY OP HYBRIDS. 



only a few more or less sterile offspring, or none at all ; 

 whilst domestic races, which differ conspicuously from 

 each other, are when united, remarkably fertile, and 

 yield perfectly fertile offspring." 



He finds it impossible to reconcile this sterility, with 

 his theory. But, he has endeavored to show, that the 

 objection may not be so conclusive against his theory, 

 as it appears to be. He essays this, in two ways, each 

 of which betrays about as cool a device as may be 

 conceived. 



He argues, (i) that the objection should not be 

 deemed conclusive, because there is an infinite num- 

 ber of degrees of fertility, and of sterility, among even 

 individuals of the same species, all of which phenomena, 

 he says, are inexplicable; and argues that, therefore, our 

 ignorance of such phenomena, deprives us of a full as- 

 surance, that the obvious and conceded import of the 

 sterility of hybrids, is the true one ! 



He argues further, (2) "that the invariable sterility 

 of first crosses between species, and of their hybrids, is 

 not a special endowment, but is incidental on modifica- 

 tions slowly impressed, by unknown means, on the re- 

 productive systems of the parent forms." 



1. It is on page 327 of his Origin of Species, that he 

 advances the first argument (?). He there exclaims, 

 " how ignorant we are on the precise causes of ster- 

 ility;" and asserts, that, in presence of all the cases of 

 lessened fertility, and of sterility, among individuals of 

 the same species, " we must feel how ignorant we are, 

 and how little likely it is, that we should understand, 

 why certain forms are fertile and other forms are ster- 

 ile when crossed." 



