THE HAMILTON ASSOCIATION. 25 



of the land from the rest, forming impassable barriers, and isolating 

 some portions of the species from the others ; this isolation would 

 act exactly as in-and-in-breeding does in domestication, giving the 

 influences of the locality time to work their utmost on the organism, 

 giving a power and permanence to its peculiarity that would affect it 

 for all time to come, and make it difficult to obliterate it, and stamp- 

 ing it with an individuality all its own. Now this isolation could 

 have the effect of producing quite opposite results in the constitu- 

 tion of different organisms, for instance, if these barriers were, after 

 a lengthened period of time removed, this form may have become 

 so localized that it would be difficult or impossible for it to survive 

 in greatly altered conditions, so that if it ventured beyond its own 

 locality it would have a struggle to exist, or might perish altogether ; 

 or it may have been so enfeebled that it would be easily absorbed 

 wheh it commingled with the forms of other localities ; or it may be 

 so strengthened that it would leave its impress on any other form of 

 the species that it commingled with, or absorb them altogether ; or 

 its pecularities might have become so consolidated and fixed in its 

 constitution that it could pass into any other locality and be but 

 little, if at all, affected thereby. Now this is not merely an imagin- 

 ary sketch, but a brief outline of processes that are actually going 

 on, in part at least, at .the present time ; and there is good /eason 

 for believing that it has been gone through with fully by the ances- 

 tors of many forms of the present, and it may be even a hundred 

 times in the life history of some of them. When once a species 

 was introduced into the world, what seems necessary to make it a 

 permanent resident for all time after, is a sufficient degree of elasti- 

 city in its constitution to enable it to accommodate itself to the 

 altered conditions as they came upon it. 



The forms ot the past, as made known to us by the geological 

 record, seem in great measure, to have perished by catastrophe : 

 indeed I do not understand how in any other way than by a 

 sudden removal of their remains from the disintegrating power of 

 atmospheric influences, their forms could have been preserved to 

 us at all. No doubt myriads of them perished in the ordinary course 

 of events, that have not left the shadow of a shade to indicate 

 to us that they have ever existed. Now, as no one catastrophe 

 would be world wide then, any mo're than at present, so whilst num- 

 bers perished suddenly in one locality, numbers would be left alone 



