Structure of the Wings of Butterflies. 330 
carried out for nearly a third of its length in the Large 
Cabbage White. In the Nemeobiide also there is a 
parallel absorption of the upper branch of the radius 
(vein iy}). 
The median series must now be left, in order briefly to 
discuss the third modification by which the evolution of 
the venation is manifested. The theoretical number of 
veins below the cubitus with its two branches, and 
between this main vein and the lower or inner margin of 
the wing, is four. Vein vi. is indicated in a few cases 
alone as a scar, generally it has departed without leaving 
a trace behind. The cross-vein in Papilio between the 
cubitus (vein v.) and vein vil. has been identified by 
Prof. Comstock with vein vi. For the reason that I am 
disposed to consider this cross-vein in Papilio as of similar 
nature to the intercalary vein between il. and iii. in the 
hindwings of Sphinx, I am scarcely prepared to endorse 
this identification at the moment. Next, we have vein vil. 
present as a true vein on both wings in the butterflies. 
Below vein vii. two abbreviated veins exist on the fore- 
wings in some moths. Of these the upper appears as a 
loop, joined by its outer end to vein vil., in one series of the 
butterflies, which show no trace of veinix. In the other 
serieS vein vill. 1s wanting, being apparently crowded 
out, whilst instead a stout, atrophied, spur-like vein is 
found to run in an opposite direction to viil., and is 
curved downwards to the inner margin, which it joins not 
far from the base of the wing. This I designate as 
vein ix. On the hindwings veins vii. and vii. are both 
present as true, long veins in that series of the butterflies 
in which vii. is alone found on the primaries. In the other 
series where 1x. is present on the forewings, vil. alone 
remains on the secondaries, whilst vill. has disappeared. 
This disappearance through specialization of vein viil. is 
accompanied by a shrinking and inward curving of the 
inner margin of the secondary. Again we are admon- 
ished of the essential uniformity in the course of these 
changes by witnessing the same occurrence in the Attacid 
genera (Lothschildia, Samia, S&c.). The mechanical 
cause of the abbreviation and degeneration of the veins 
below vil. on the primaries may lie in the friction of the 
edges of the fore and hindwings. Above the radius on 
the primaries there is a single subcostal vein (u.) tending 
to split at the base in Thais. Fur ther, there is a vein- 
