184 ORIGIN OF SPECIES 



already assigned (namely from what we know of the actual 

 distribution of closely allied or representative species, and 

 likewise of acknowledged varieties), exist in the intermediate 

 zones in lesser numbers than the varieties which they tend to 

 connect. From this cause alone the intermediate varieties 

 will be liable to accidental extermination; and during the 

 process of further modification through natural selection, 

 they will almost certainly be beaten and supplanted by the 

 forms which they connect ; for these from existing in greater 

 numbers will, in the aggregate, present more varieties, and 

 thus be further improved through natural selection and gain 

 further advantages. 



Lastly, looking not to any one time, but to all time, if my 

 theory be true, numberless intermediate varieties, linking 

 closely together all the species of the same group, must as- 

 suredly have existed ; but the very process of natural selec- 

 tion constantly tends, as has been so often remarked, to ex- 

 terminate the parent-forms and the intermediate links. Con- 

 sequently evidence of their former existence could be found 

 only amongst fossil remains, which are preserved, as we shall 

 attempt to show in a future chapter, in an extremely imper- 

 fect and intermittent record. 



On the Origin and Transitions of Organic Beings zvith 

 peculiar Habits and Structure. — It has been asked by the 

 opponents of such views as I hold, how, for instance, could 

 a land carnivorous animal have been converted into one with 

 aquatic habits ; for how could the animal in its transitional 

 state have subsisted? It would be easy to show that there 

 now exist carnivorous animals presenting close intermediate 

 grades from strictly terrestrial to aquatic habits ; and as each 

 exists by a struggle for life, it is clear that each must be well 

 adapted to its place in nature. Look at the Mustela vison 

 of North America, which has webbed feet, and which re- 

 sembles an otter in its fur, short legs, and form of tail. Dur- 

 ing the summer this animal dives for and preys on fish, but 

 during the long winter it leaves the frozen waters, and preys, 

 like other pole-cats, on mice and land animals. If a different 

 case had been taken^ and it had been asked how an insectiv- 

 orous quadruped could possibly have been converted into ■ 

 a flying bat, the question would have been far more 



