Chap. VI. ORIGIN OF SPECIES. 261 



posed parent also seems to have been modified, and then 

 the demonstration is not so clear, for some of the links 

 in the chain of variation are wanting. The process of 

 origination of a species in nature, as it takes place suc- 

 cessively, must be ever perhaps beyond man's power to 

 trace, on account of the great lapse of time it requires. 

 But we can obtain a fair view of it by tracing a variable 

 and far-spreading species over the wide area of its 

 present distribution ; and a long observation of such will 

 lead to the conclusion that new species in all cases must 

 have arisen out of variable and widely-disseminated 

 forms. It sometimes happens, as in the present instance, 

 that we find in one locality a species under a certain 

 form which is constant to all the individuals concerned ; 

 in another exhibiting numerous varieties ; and in a third 

 presenting itself as a constant form, quite distinct from 

 the one we set out with. If we meet with any two 

 of these modifications living side by side, and maintain- 

 ing their distinctive characters under such circumstances, 

 the proof of the natural origination of a species is com- 

 plete : it could not be much more so were we able to 

 watch the process step by step. It might be objected 

 that the difference between our two species is but 

 slight, and that by classing them as varieties nothing- 

 further would be proved by them. But the differences 

 between them are such as obtain between allied species 

 generally. Large genera are composed, in great part, 

 of such species ; and it is interesting to show how the 

 great and beautiful diversity within a large genus is 

 brought about by the working of laws within our 

 comprehension. 



