The President's Address. 109 



other groups would thus be encouraged to follow it up by 

 catalogues of their own special objects of study. There is 

 yet another point to be mentioned in connection with the 

 preparation of such lists, and that is the possible occurrence 

 of local variation. Of course we cannot expect in such a 

 limited area to find many or well-marked instances of this 

 phenomenon, but it nevertheless seems to me desirable to 

 make a most careful comparison, especially in the case of 

 variable species, between series from the various portions 

 of our own county and series from other parts of the 

 country and from the Continent. This is the more espe- 

 cially desirable with common and variable species which 

 extend to our marsh-fringed coast. Mr. H. W. Bates tells 

 us that in the Amazon Valley the butterflies undergo modi- 

 fication to such an extent that many species appear to 

 change into a distinct local race in every fresh district. It 

 is obviously useless to look for such striking instances in a 

 small island like ours, where there are but few facilities for 

 isolation, and whero local variation is consequently oblite- 

 rated by free intercrossing. But there is no reason why 

 the phenomena which occur in the tropics en grand should 

 not appear in this country en petit, and a searching exami- 

 nation of long series of specimens in the manner suggested 

 may possibly result in the discovery of some positive 

 evidence in this direction. 



The next suggestion is one that appeals to our botanists. 

 We have had recently added to our Forest large tracts of land 

 formerly under cultivation, but now being gradually recon- 

 verted into forest land. It appears to me that we have 

 here a natural experiment going on of which we should 

 take advantage : we can surely learn something of the 

 manner in which a forest spreads by keeping a careful 

 watch upon such tracts, noting the plants that from time 

 to time make their appearance, and by this means recording 

 the encroachment of species, and observing the effects of 

 that struggle for life which is one of the prime factors in 

 the evolution of living forms. 



One other suggestion, and I have finished. Now that 

 our sylvan head-quarters have so much increased in extent 



