122 THE AMERICAN NATURALIST. (VOL: XXXIII. 
is not the slightest difficulty in tracing the homologies of the 
veins. In one the radial sector and the media contain well- 
` preserved trachez ; in the other there is not the slightest trace 
of a trachea in these veins. On the other hand, in the latter 
the cubital trachea is forked, one of the branches traversing 
vein Cz2; while in the former the cubital trachea is simple, 
there being not the slightest indication of a trachea in vein C72. 
The basal connections of the trachea of the wing are very 
different from what we have seen elsewhere. In the Plecoptera 
there are two distinct groups of tracheze which enter the wing ;! 
the same is true of certain cockroaches ;? in all other forms 
Fic. 70.— The tracheation of a wing of a May-fly nymph. 
that we have studied, except the May-flies, a transverse basal 
trachea connects these two groups, and from this transverse 
trachea (transverse in relation to the wing, but longitudinal in 
relation to the body) the principal trachez of the wing extend 
more or less nearly at right angles to it.? In the May-flies a 
single trachea arises from the principal longitudinal trachea of 
one side of the thorax, and, after giving off a branch to the 
corresponding leg, passes directly to the base of the wing. 
Here it divides into several branches which continue in approxi- 
mately the same direction and become the principal trachez 
of the wing. 
In some cases this trachea extends into the wing before it 
divides. But in other forms, which we regard as more general- 
1 American Naturalist, vol. xxxii, p. 238, Fig. 8; p. 239, Fig. 9. 
2 Loc. cit p. 773, Fig. 56. 8 Loc. cit., p. 772, Fig. 54. 
