Darwiiis Theory of Sexual Selection 183 



Darwin compares them to the horns of stags and of the 

 rhinoceros. They "are wonderful from their size and 

 shapes." Darwin offers the following conjecture as to their 

 meaning: "The extraordinary size of the horns, and their 

 widely different structure in closely allied forms, indicate 

 that they have been formed for some purpose ; but their 

 excessive variability in the males of the same species leads 

 to the inference that this purpose cannot be of a definite 

 nature. The horns do not show marks of friction, as if used 

 for any ordinary work. Some authors suppose that as the 

 males wander about much more than the females, they re- 

 quire horns as a defence against their enemies ; but as the 

 horns are often blunt, they do not seem well adapted for 

 defence. The most obvious conjecture is that they are 

 used by the males for fighting together ; but the males have 

 never been observed to fight ; nor could Mr. Bates, after a 

 careful examination of numerous species, find any sufficient 

 evidence, in their mutilated or broken condition, of their hav- 

 ing been thus used. If the males had been habitual fighters, 

 the size of their bodies would probably have been increased 

 through sexual selection, so as to have exceeded that of the 

 females ; but Mr. Bates, after comparing the two sexes in 

 above a hundred species of the Copridae, did not find any 

 marked difference in this respect amongst well-developed 

 individuals. In Lethrus, moreover, a beetle belonging to 

 the same great division of the lamellicorns, the males are 

 known to fight, but are not provided with horns, though their 

 mandibles are much larger than those of the female." 



" The conclusion that the horns have been acquired as orna- 

 ments is that which best agrees with the fact of their having 

 been so immensely, yet not fixedly, developed, — as shown 

 by their extreme variability in the same species, and by their 

 extreme diversity in closely allied species. This view will at 

 first appear extremely improbable ; but we shall hereafter 

 find with many animals standing much higher in the scale, 



