No. 384.] THE WINGS OF INSECTS. QII 
there is not space for details, but these are the less necessary 
because the junior author will shortly publish elsewhere an 
extended paper upon the venation of this order. It may be 
remarked, however, in passing, that the tendency throughout the 
order is toward vein multiplication. Additions are made upon 
both sides of several principal branches, and they conform to no 
one simple type. These new branches are preceded by trachez ; 
but there are other interpolated veins developed for mechanical 
advantage quite independently of the tracheze and cutting across 
them. 
The radial sector is unique in form as well as in position. 
All the peculiarities of this intricate venation have arisen out 
of the necessity for making all the veins individually useful : 
and those dragon flies which have been most successful in dif- 
ferentiating between the added veins are among the fleetest of 
winged creatures. 
