Page - 184 - in The Origin of Species

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 varietieswhichthey 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 thelongwinter 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