152 Animal Life and Intelligence, 



round variation, there is nothing to give these non-useful 

 specific characters fixity and stability, nothing to prevent 

 their being swamped by intercrossing. If, however, on the 

 hypothesis of combination, we have definite organic com- 

 pounds, instead of, or as well as, mere hereditary mixtures ; 

 if, in other words, variations take definite lines determined 

 by the laws of organic combination (as the nature and 

 properties of chemical compounds are determined by the 

 laws of chemical combination) , then this difficulty disappears. 

 There is no reason why a neutral divergence — one neither 

 useful nor deleterious — should be selected or eliminated. 

 And if its direction is predetermined, there is no reason 

 why it should not persist, though, of course, it will not be 

 kept at a high standard by elimination. It has again and 

 again been pointed out as a difficulty in the path of natural 

 selection that, in their first inception, certain characters or 

 structures cannot yet be of sufficient utility to give the 

 possessor much advantage in the struggle for existence. 

 If, however, these be definite products of organic combina- 

 tion, this difficulty also disappears. So long as they are 

 not harmful, they will not be eliminated, and by fortunate 

 combinations will progress slowly until natural selection 

 gets a hold on them and pushes them forward, developing 

 to the full the inherent tendency. Finally, we must notice 

 that, on this hypothesis, our conception of panmixia, or 

 intercrossing, would have to be modified. As generally 

 held, this doctrine is based upon hereditary mixture, not 

 organic combination. It is a doctrine of means and 

 averages. There is a good deal of evidence that inter- 

 crossing does not, at least in all cases, produce mean or 

 average results. And according to the hypothesis of 

 organic combination, it need not always do so. According 

 to this hypothesis, then, divergent modifications might arise 

 and be perpetuated without the necessity of isolation. 

 Sterility might result from the fact that divergence had 

 been carried so far that organic combination was no longer 

 possible ; reversion, due to intercrossing, from the fact 

 that combinations long rendered impossible by the isolation 



