specific modifications of Japan Carahi. oil 



Pericopis is a moth, and that Heliconius is a butterfly, the 

 separation between the two in classification is wide 

 indeed ! But the species, after separating, come together 

 again, inhabit the same glens, live under the same 

 physical conditions, assume the same position in flight 

 and at rest, and, by steps which I think we can trace, 

 similarity of colour and pattern of wing follow. For 

 they both still possess in a certain degree the same 

 internal physiological organisation with which they were 

 endowed before their separation, and this, too, in a com- 

 paratively little modified state. It is a point which 

 confirms this view, and carries conviction to my mind, 

 that species of this kind are always found living together, 

 and are subject, therefore, to the same physical con- 

 ditions. And Nature, acting on a physiological organism 

 not very dissimilar, can produce no other result but 

 similarity of appearance and structure. The conditions 

 I refer to are external conditions, which would, in the 

 ordinary nature of things, act first on the outer characters 

 of a species, — wings, colour, antennae, and so forth, — 

 while a longer time would be required to modify the 

 more vital parts. Many allied moths resemble the 

 butterflies they associate with, species by species, and 

 I think the above is the explanation of the phenomenon. 

 In the Coleoptera there are also numerous instances. If 

 an African moth resembled an American butterfly, the 

 case would be different ; but, I should still say, that 

 similar conditions of life produced similar results in both 

 continents. 



After thinking what insects have passed through, it is 

 natural to turn to the future. But in that we must not 

 assume that existing species can be modified only by a 

 process similar in kind to that which produced them, for 

 then we could not assign to them any continued exist- 

 ence ; but this we may say, that all forms, even those 

 hard and comparatively permanent species now existing 

 in Europe, will through all time continue to be modified 

 under the causes which will be produced by agencies now 

 in operation. We cannot bring the same forces to bear 

 on our domestic animals which Nature has used in 

 forming the parent stock. All we can do is to compare 

 domestic modifications with those variations which are 

 now taking place in wild animals, and this is exceedingly 

 difficult, because the rate at which modifications proceed 

 in the two is so different. 



TRANS. ENT. SOC. 188:2. PART IV. (dEC.) 3 X 



