1898] CLASSIFICATION OF THE DAY BUTTERFLIES 93 



radius of the forewings, and we can here notice the grades of ab- 

 sorption by which this change is finally accomplished. In the pre- 

 sumed ancestors of lepidoptera the network of the wing was more 

 complex, and the general tendency in the lepidoptera would be thus 

 evidently towards a simplification of the neuration. The second direc- 

 tion is apparently of lesser importance than the first, for the reason 

 that it is confined by its nature to the forewings of a minority of 

 the lepidoptera ; Avhereas what we have called the first direction is 

 now active everywhere on both pairs, and is seemingly indicative of 

 a process inaugurated on the hindwings, to be echoed by the fore- 

 wings. The second direction, it may be hypothetically considered, 

 has completed its task with the hindwings of such lepidoptera 

 which have the radius already reduced to a single unbranched 

 vein. 



To summarise the principal openings through which I have tried 

 to carry the working theory of the evolution of the neuration beyond 

 what had been previously attained : — 



1. I try to show that the suppression of the media is the 

 result of a continuous movement, variously expressed by the host of 

 forms, which, after absorbing the connection of the system with the 

 base of the wing and thoracic source of supply, next disintegrates 

 the cross-vein, and finally distributes the outside branches of the 

 media between radius and cubitus. I designate and explain the 

 process by which the cubitus becomes three or four branched. 



2. I try to show that the piece of the cross-vein closing the cell 

 and lying between the branches of the media and either radius or 

 cubitus, becomes functionally the base of the branches in their new 

 position after the disappearance of the central connecting portion of 

 the cross-vein. Its formed morphological character as a portion of 

 the cross-vein becomes gradually lost, the angles softening, and all 

 trace of its former condition becoming obliterated. This process 

 may be clearly traced on the forewings of Lycacna, Thccla, Zcphyrus, 

 and of Augiades sylvanus. 



3. I try to show that the absorption of the radial branches is 

 due to a sporadic movement upon separate lines of descent, and that 

 this movement is probably reminiscent of the similar action which has 

 apparently very generally been fully carried out on the hindwings 

 of most existing lepidoptera. It is questionable whether we can 

 assume that a corresponding simplification can be attained by the 

 radius of the forewings, and this from the different conditions of 

 the front portion of the forewings as compared with that of the 

 hindwings. There seems ground for believing that the absorption 

 of the media has been commenced at a later period than the 

 reduction of the branches of the radius. 



4. I try to show that the evolutionary movements are, generally 



