1912] Homologies in the Wing-veins of May-flies 99 
highly probable that the radial sector is present in May-flies. 
and that both the sector trachea and the vein Rs have been 
stranded on M, and have left no positive trace of their origin. 
7 TVT TE 
Fig. 4. WINGS OF EPHEMERA. 
A. Previous interpretation of radius and media. 
B. Present interpretation of radius and media. 
Radius and its supposed sector are represented by dots and dashes, media is 
represented by a series of dots. 
Such an interpretation involves important changes in the 
nomenclature of the veins in the radial and medial regions. 
These changes may be clearly seen by comparing the wings A 
and B in the accompanying figure (Fig. 4). 
The Cubital Trachea. 
In Chirotonetes (Pl. V,. Fig. 1) the cubito-anal and medial 
tracheae diverge and then run nearly parallel for ashort distance. 
In this region the anal tracheae branch off (Pl. V, Fig. 1, lst A). 
The cubital trunk then bends forward again toward the medial 
trachea, making a prominent bend just below the first fork of 
