334 OHIO STATE ACADEMY OF SCIENCE 
ated by immense gaps in geological time, all of the mechanism of a 
tracheated flying arthropod. 
That they were insects, that they had a tracheal respiration and 
that they were capable of flight must be accepted else we may as 
well call in question the w hole mass of knowledge based on fossil 
remains and which we so confidently accept as indubitable history 
of the forms of life which peopled the earth in past ages. 
So much for the antiquity of the organ which we have in dis- 
cussion and we may perhaps give pause for a moment to think how 
long since and by what lowly creatures was the problem of aerial 
navigation solved, a problem so attractive yet so elusive to the 
powers of man. How then was the problem solved, what were 
the factors conspiring to provide for flight ? 
It is hardly necessary to remark that the wing of an insect is 
a totally different structure from the wing of a bird. The most 
superficial observation as well as the most elementary knowledge 
of anatomy is sufficient for this. Their minute structure and the 
process of their growth are, however, less familiar and in order 
to secure a firm foundation for the discussion of the mode of 
origin we must show something of this fundamental structure and 
its agreement in different kinds of insects —a bit of dry anatomy, 
a skeleton on which we may hang our threads of theory. 
The insect wing is fundamentally a sack the membranous walls 
of which are supported by a series of stiff rodliike “nerves” or 
“veins”. <A sacklike structure is easily seen in the expanding 
wings of a moth or butterfly. As the rodlike supports fit to each 
other above and below the fluid not used in the formation of the 
wing is withdrawn into the body and the membrane hardens so no 
separation between the upper and lower layer is noticeable. So 
much may easily be accepted as common to all insects. Is there 
anv similar uniformity with regard to the number and arrange- 
ment of the veins? 
In the different orders of insects we have quite diverse apparent 
arrangement so that comparison of a mature cockroach, dragon fly, 
Cieada, house fiy, beetle, butterfly and bee would show what appear 
» be very different patterns of veins. So different indeed that 
eee ce have applied very different sets of names to the 
various nerves and while various attempts have been made _ to 
establish uniform systems, such attempts have been largely unsuc- 
cessful. mise recently through elaborate studies of Professors 
Comstock and Needham this uniformity has been much_ better 
established and we can say with very great assurance that the wing 
structure of all insects is reducible to a common plan or, to carry 
out the logical conclusion from this, that the wings of all insects 
are derived from one ancestral form. 
I need not here burden you with the technical names of these 
structures or of the detailed statement of their homology. Refer- 
