60 THE GENESIS OF SPECIES. [CHAP. 



ficient to explain the incipient, infinitesimal beginnings of 

 structures which are of utility only when they are consider- 

 ably developed. 



Let us consider the mammary gland, or breast. Is it 

 conceivable that the young of any animal was ever saved 

 from destruction by accidentally sucking a drop of scarcely 

 nutritious fluid from an accidentally hypertrophied cutaneous 

 gland of its mother ? And, even if one was so, what chance 

 was there of the perpetuation of such a variation ? On the 

 hypothesis of " Natural Selection " itself, we must assume 

 that up to that time the race had been well adapted to the 

 surrounding conditions ; the temporary and accidental trial 

 and change of conditions, which caused the so-sucking young 

 one to be the " fittest to survive " under the supposed cir- 

 cumstances, would soon cease to act, and then the progeny 

 of the mother, with the accidentally hypertrophied, seba- 

 ceous glands, would have no tendency to survive the far 

 outnumbering descendants of the normal ancestral form. 

 If, on the other hand, we assume the change of conditions 

 not to have been temporary but permanent, and also assume 

 that this permanent change of conditions was accidentally 

 synchionous with the change of structure, we have a coin- 

 cidence of very remote probability indeed. But if, again, 

 we accept the presence of some harmonizing law simulta- 

 neously determining the two changes, or connecting the 

 second with the first by causation, then, of course, we re- 

 move the accidental character of the coincidence. 



Again, how explain the external position of the male 

 sexual glands in certain mammals? The utility of the 

 modification, when accomplished, is problematical enough, 

 and no less so the incipient stages of the descent. 



As was said in the first chapter, Mr. Darwin explains 

 the brilliant plumage of the peacock or the humming-bird 

 by the action of sexual selection : the more and more bril- 

 liant males being selected by the females (which are thus 



