THE DIRECT STRUGGLE BY COMBAT. 363 



which it is more or less successfully conducted by this or that 

 individual, but also on the reaction, of those very conditions for 

 the possession of which the struggle took place. An example 

 will here be appropriate. Supposing that t\vo suitors of the 

 same distracting beauty agreed to fight a duel for the possession of 

 the fair one, the surviving lover could be designated as fortunate 

 only in the event of its having been understood that he would 

 thus win the lady's affections. This example illustrates, with a 

 little exaggeration of course, the indisputable fact that in every 

 case of a competition between two animals for one and the 

 svinie object, this object itself must have a certain, and indeed a 

 selective, influence on the ultimate results of the contest. Sup- 

 posing that two larvae of dissimilar species of Bopyrus should 

 meet at the entrance of the same branchial cavity and begin a 

 struggle for the possession of it, under certain circumstances the 

 parasite to which the cavity did not properly belong might 

 come off victorious, but this would avail it but little, since it 

 could not live in the branchial cavity of which it had obtained 

 possession. The larva of an insect boring and living in wood 

 might perhaps in the same way be able to conquer another 

 which was accustomed to live and bore in leaden bullets ; but 

 it is extremely doubtful whether the wood-borer would thus be 

 enabled to live in the lead. Exactly the same thing occurs 

 between two individuals of the same species. We might 

 perhaps be inclined to assume thtrt the tendency of two indivi- 

 duals to possess themselves of the same object was of itself a 

 satisfactory and sufficient proof that both animals must be 

 equally well fitted for the condition of life in dispute, but 

 nothing could be further from the truth than this assumption. 

 If, for instance, two men contend for the same office, a presi- 

 dency or a professorship, under all the given circumstances one 

 will be better fitted for the post than the other, and if among 

 men this better qualification were the sole condition of selection 

 the post would always be filled by the best candidate; the post 

 itself would effect the selection by the qualifications which it 

 demands. It is precisely the same with animals. "When two 

 lions or wolves fight for a prey, the stronger will undoubtedly 

 win; but if the conqueror hapj>ens to liave a bad digestion, in 



