124 THE AMERICAN NATURALIST.  [VoL. XXXIII. 
evolved from a wing of either the ephemerid or neuropterous 
type. After a wing had been strengthened by many cross- 
veins, it is not probable that these should disappear with the 
exception of the few to which we have applied names! in 
so many different orders, in so nearly an identical manner. 
Forms with reduced venation occur in most of the orders, but 
the results of these independent reductions differ greatly from 
each other. It is necessary, therefore, to examine again the 
paleontological evidence. 
The great preponderance of many-veined wings in the Car- 
boniferous rocks is probably due to the fact that doubtless then, 
as now, insects with many wing-veins were the ones that lived 
near water, and were, therefore, the ones most likely to be pre- 
served as fossils. 
Another point which should be taken into account is that, 
notwithstanding the great antiquity of the Carboniferous times, 
it was a comparatively late period in the history of insects, 
for winged insects appeared in the Silurian. We are carrying 
our investigations back only a step, although it is a long one, 
towards the period when wings were first developed by studying 
Carboniferous fossils. 
Unfortunately, our knowledge of Silurian insects is meager. 
Moberg has figured an insect from the upper part of the lower 
Silurian ; and Brongniart has figured and described a wing from 
the middle Silurian sandstone of Calvados, France. This we 
believe is all that is known regarding the insect fauna of the 
Silurian ; and when we take into account the immensity of the 
period of time occupied by the deposition of the Silurian rocks, 
we are forced to admit that we know almost nothing regarding 
the older insects. 
Of the Devonian insects, the remains of several are known. 
Those which are best preserved are Homothetus fossilis (Fig. 
71), Xenoneura antiquorum (Fig. 72), and Platephemera antiqua 
(Fig. 73). (The figures given here are reproduced from Plate 
VII of Mr. Scudder’s Pretertiary Insects.) A glance at these 
figures will convince the reader that the insects of the Devonian 
times varied greatly in the structure of their wings. For 
; 1 American Naturalist, vol. xxxii, pp. 233, 234- 
