362 EEV. J. T. GTJLICK ON 



and Nova Scotia on the east, over New England, Canada, 

 the region of the lakes, away to the north-west, toward the 

 confines of Alaska. It will be observed that the area of distri- 

 bution of B. Archippus includes the whole of that of B. Astyanax 

 and a large portion of that of B. Arthemis ; while the areas of 

 B. Astyanax and B. Arthemis overlap along the whole northern 

 border of the territory occupied by B. Astyanax. This area of 

 overlapping distribution in which the three species are associated 

 is about a thousand miles in length, and from one hundred to 

 one hundred and fifty miles in width. 



Forms of Segregation tliat separate B. Archipj^usj^row 

 B. Astyanax and B. Arthemis. 



It is evident that, in the present condition of distribution, 

 geographical barriers and territorial separation have nothing to 

 do with the integrity of B. Arcliippus as a separate species. In 

 other words, it is not under the influence of Geographical or 

 Local Segregation. Whatever may have been its past history, 

 these certainly are not the causes that at present prevent it 

 from interfusing with other species of Basilarcliia with which it 

 is associated. 



Again, Seasonal Segregation seems to have but little influence; 

 for, though B. ArcMpjJus seems to appear 15 or 20 days earlier 

 than the other species, the remainder of the breeding-season, 

 which extends over many weeks, is coincident. 



The habits and feeding instincts of this species must tend to 

 separate it somewhat from B. Arthemis, for this latter species 

 frequents forest-regions, especially when elevated and hilly, 

 while B. Archippus is found in the open country in fields and 

 meadows, especially in low levels. The eggs of B. Arthemis are 

 chiefly deposited on the species of birch and willow that are 

 found on the highlands ; while the eggs of B. Archippus are 

 chiefly deposited on the willows and poplars found on the low- 

 lands, though on the White Mountains it occasionally extends its 

 range to as high levels as B. Arthemis. There is therefore 

 between these species a slight degree of Industrial Segregation ; 

 hut this partial segregation does not prevent their being often 

 found in the same fields, and unless held apart by sexual instincts 

 and by partial infertility, hybrids, which are now very rare, would 

 be very common. 



We are therefore lead to believe that diversity of sexual 



