75 



a rule, well denned, though frequently superficially similar. 

 But there is one characteristically holarctic series of Hes- 

 peridae — the series of Pamphila comma — and here at once we 

 meet with innumerable local races or weak species, with 

 difficulty to be separated from one another. So in Lyccena 

 the holarctic group of pseudargiolus and its allies is especially 

 polymorphic. When we come to the typically holarctic 

 genera, such as Argynnis, we find a wilderness of plastic 

 forms, which may be called species or varieties according to 

 the taste of the student. 



It thus happens that for the evolutionist temperate regions, 

 lately subject to glacial desolation, are in many respects more 

 interesting than the luxuriant tropics. Here, especially, are 

 species in the making ; here is Nature's kitchen, and the cook 

 at work. In the tropics, on the other hand, we often find 

 more numerous and more finished products and wonderful 

 adaptations, the origin of which is past our comprehension. 

 The naturalist in South America might well think species 

 were created as he found them ; the naturalist of the 

 northern United States could hardly imagine such a thing, 

 unless convinced on a priori grounds. 



Yet when changes have occurred in tropical lands we find 

 such phenomena as are common in the north. The snails 

 of the Greater Antilles, islands that have undergone great 

 changes of level in recent geological periods, are almost 

 as confusing as the North American Argynnids. So it 

 seems we may in some measure learn the past history of a 

 group by studying its species. If the species are well defined 

 and show elaborate adaptations to the environment, the 

 group has long existed under relatively uniform conditions. 

 If, on the other hand, the species are defined with difficulty 

 and connected by numerous races, it may be presumed that 

 the environment of the group has changed in recent times, 

 and especially that it is undergoing expansion and differen- 

 tiation in new territory. In northern regions the retreat of 

 the ice has exposed much such territory ; in the Antilles it 

 has been the elevation of the land ; in other cases a type 

 may have found new lands by migration, and may thus 

 exhibit incipient new species in the midst of a stable ancient 

 fauna. As an example of the last-mentioned class may be 

 mentioned Danais berenice jamaicensis in Jamaica, as against 

 the old Jamaican type Papilio homerns. 



In the ensuing discussion Mr. Carrington remarked on 

 the tendency with some naturalists to specify weak species, 

 and to allow but little for local circumstances and environ- 



