Natural Selection of Species. 113 



fer them to fall into disuse without their deterioration and decay. So 

 we may suppose that all the wolves by reason of their hunting the rab- 

 bits would become possessed of keener organs of sight, smell and hear- 

 ing, more vigorous legs, and larger cerebral hemispheres than they had 

 at first. On the other hand, the rabbits, by the exercise of like faculties 

 for their self preservation, develop their organs of sense, locomotion, 

 and reflection. The reproductive qualities of the rabbits are very great. 

 Their numbers double at least every three months and if unchecked 

 they would soon reach the limit of their food suppty on our island. But 

 of course their increase is checked by the inroads of the wolves. Every 

 day the wolves select certain of the rabbits for their dinner, a selection 

 governed by the inexorable laws of necessity. For each wolf takes 

 such rabbit as he can get, and the captured ones will obviously be those 

 least alert, those having the dullest senses, those least active of limb, 

 those most debilitated by disease or worn out by age, and those most 

 conspicuous by reason of their color or their odor. This daily selection 

 of the weak and inferior to die is also a selection of the strongest and 

 best to live and transmit their superior qualities -to their heirs and suc- 

 cessors. Thus the selection by the wolves tends to improve the stock of 

 rabbits, just as the limit of their food supply would tend to improve 

 them if there were no wolves. For as soon as the limit of the food sup- 

 ply were approached there would be a struggle among the rabbits them- 

 selves for their food, the strongest and most active obtaining it and 

 leaving the weaker to succumb to want. 



A rabbit pursued by hounds has been known to transfer the pursuit 

 to another rabbit. He would lead the chase near the retreat of rabbit 

 number two, and suddenly leaping upon his seat would crowd No. 2 off 

 and compel him to take flight before the dogs, while No. 1 remained 

 unobserved on the usurped seat. 



Notwithstanding the rapidity with which rabbits increase it is not 

 great enough to allow for the unchecked increase of wolves. Say the 

 latter double every year while the rabbits increase eight fold. But a 

 wolf must have at least 100 rabbits a year or starve ; so for each new 

 wolf there should be 100 new rabbits, and there are only one-twelfth 

 that number. The result of the struggle among the wolves for this 

 limited food supply must result in the same way as among the rabbits, 

 in selecting the most wily, alert, observing and active wolves for sur- 

 vival and the transmission of their qualities, while the hmdermost must 

 always be the ones to succumb. The details of the struggle for exist- 

 ence are of various kinds/ Those that fail to secure food starve out- 

 right. Others are killed in contests to maintain the ownership of what 

 they have obtained. Others are reduced to a condition incompatible 

 with the production of vigorous offspring and so run out. 



