REPORT OF THE STATE ENTOMOLOGIST I907 233 



the first fork of the media, the fork of cubitus, the radio-medial 

 cross vein, and the medio-cubital cross vein. Primitively the cord 

 was very much zigzagged in and out, and secondarily it often be- 

 comes quite straight, but whatever its shifts of position, its ins and 

 outs, it is always clearly recognizable, and the parts just cited are its 

 essential parts. It is always attached to vein R^, but there is the 

 most extraordinary diversity in its mode of attachment. It may, 

 with the aid of the radial cross vein, be slung from R^ upon a truss 

 of equal arms (the arms being the base of Rs and portions of 

 R^+^, see plate 29) ; or, the distal arm may be shortened, as in a host 

 of forms (as indicated in the diagram fig. 11) ; or the proximal arm 

 may be shortened as in Dolichopeza [pi. 16, fig. 5] ; or both arms may 

 be shortened simultaneously as in Cryptolabis [pi. 30, fig. i] and 

 Peripheroptera [pi. 28, fig. 4] or the radial cross vein may come into 

 a position of increased responsibility as in Conosia [pi. 21, fig. 5] 

 or may be brought into direct line with the cord, as in Paratropeza 

 [pi. 21, fig. 4] ; or, the radial cross vein may atrophy, as in a host 

 of forms, leaving the cord supported by the base of the sector alone ; 

 or, the opposite thing may happen; the tip of R^ may turn forw^ard 

 and fuse with the tip of R^, thus eliminating the radial cross vein, 

 with the usual result of leaving a very strong union in its place ; and 

 the vein R-^ may follow it, and the base of the sector may atrophy, 

 leaving the cord slung from the radius by R^^ alone, as in Scambo- 

 neura [pi. 16, fig. 6]. But, these shifty parts aside, be it noted that 

 the foremost fixed point in the cord is the first fork of the radial 

 sector, and the hindmost point is the fork of cubitus, and between 

 these two points it had primitively a zigzag, in and out course, 

 which has been corrected, shortened and improved chiefly by the 

 shortening of these forks, and the divarication of their branches. 



This path of union traverses the cell ist M^. — one might say, is 

 interrupted by that cell. Probably the cell ist M^ and probably the 

 entire median vein with it, might well have been dispensed with, 

 for the more successful of the Diptera have either eliminated it, 

 or brought it into quite new relations to adjacent veins. But it 

 was present, and its principal fork was interposed squarely between 

 the forks of the adjacent veins. That is the burden of inherit- 

 ance; for the wing was not made out of dreams, as some might 

 have us think — out of hypothetical a priori fitnesses — out of 

 vacancy, to which parts might be added in a rational and beautiful 

 manner, but out of a fold of hypodermis, traversed by branching 

 tracheae, and secreting chitin about them and between them. The 



