1 64 TRANSITIONS OF ORGANIC BEINGS. 



a short duration. For these intermediate varieties will, 

 from reasons already assigned (namely from what 

 we know of the actual distribution of closely allied 

 or representative species, and likewise of acknowl- 

 edged 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 at all time, if 

 my theory be true, numberless intermediate varieties, link- 

 ing closely together all the species of the same group, must 

 assuredly have existed; but the very process of natural 

 selection constantly tends, as has been so often remarked, 

 to exterminate the parent-forms and the intermediate links. 

 Consequently evidence of their former existence could be 

 found among fossil remains, which are preserved, as we 

 shall attempt to show in a future chapter, in an extremely 

 imperfect and intermittent record. 



01^ THE OKIGIN" AND TKANSITION OF ORGAN"IO BEIi^GS 

 WITH PECULIAE HABITS AKD 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 sub- 

 sisted? 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 

 vision of North America, which has webbed feet, and 

 which resembles an otter in its fur, short legs, and form 

 of tail. During 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 



