328 Difficulties of Davwimsm. [July, 
remarkable for protuberances which in colloquial phrase 
are known as horns. The parts in question differ most es- 
sentially from the horns of Mammalia: they are integral 
portions of the skeleton, and, instead of being confined to 
the head, they are in many—if not in most—cases develop- 
ments of the thorax, a part analogous to the shoulders and 
upper portion of the back in vertebrate animals. Hence 
they are incapable of motion, except in common with the 
entire body of the inse¢t: they are so far sexual in character 
that they are almost confined to the males, and they vary 
exceedingly in magnitude among individual specimens of 
one species found in the same locality. If their presence is 
to be explained by Natural Selection they must have some 
reference to the habits and functions of the insect. But to 
what habits or functions? They are evidently not organs 
of sensation; as little can they serve in procuring food. 
For weapons—either against enemies of the same or of 
different species—they are not adapted, in some cases by 
reason of their position and direction, and in all by their 
very imperfect mobility. As to locomotion, they must be 
rather an impediment than an aid. Imagine an insect 
boring into mould or decayed wood, creeping under fallen 
trees, or through twigs and the roots of herbage, whilst en- 
cumbered with horns like those of Hoplites Pan, Dynastes 
dichotomus, or the Golof@. In short, we are unable to con- 
ceive what purpose they serve. We find promiscuously 
individuals with highly developed horns, and others in which 
these parts are almost obsolete. Nor can we say that either 
kind appears to have any advantage over the other. If, 
e.g., we examine a plot of ground in Central or Southern 
Europe where the spent bark from tanneries has been depo- 
sited, we shall find male specimens of Oryctes nasicorms with 
large and with small horns, respectively in about equal 
numbers. Now if any decided benefit accrued from either 
conformation we might expect that it would rapidly prepon- 
derate, and that the other form would, in the course of 
Natural Seleétion, have become rare, or be eliminated alto- 
gether. Similarly, if the large-horned males were regarded 
with especial favour by the females, we should anticipate 
that the small-horned type would gradually disappear by the 
precess of Sexual Selection. 
MacLeay, Swainson, and their followers, explain the 
horns of the Dynastide, or indeed of the entire Sapropha- 
gous Lamellicornes, on the principle that they represent the 
Ruminant Mammalia, and that, as the one group is horned, 
the other—whose function is to bury the excrements of the 
