224 



THE EVOLUTION THEORY 



show that the personal excellences do actually function as a means 

 of exciting and attracting, if any one should still doubt it. 



All the distinguishing characters of the male which we have 

 hitherto considered have had reference to gaining the favour of the 

 female, but there are many other secondary sexual characters which 

 are employed in quite a different manner to secure possession of the 

 female. I have already mentioned that in many butterflies the males 

 possess a much larger organ of smell. The antennae of the males of 

 numerous beetles, such as the cockchafer and its relatives, are also 

 much larger, and furnished with much broader accessory branches, 

 than those of the female, and the same is the case in many of the 

 lower crustaceans, like the large transparent Daphnid of our lakes, 

 Leptodora hycdina. Here the anterior antenna bears (Fig. ^6, 

 A and 5, at') olfactory filaments; in the female this appendage is small 



^^^^ "' 



Fig. 56. Leptodora hyalina. A, head of the male. B, head of the female. 

 All, eye. g. opt, optic ganglion, gh, brain, at' , first antenna with olfactory 

 filaments ri and ri'. sr, oesophageal nerve-ring, n, nerve, m, muscles. 



and stump-like, while in the male {A) it grows to a long, somewhat 

 curved rod, which is extended obliquely into the water, and in addition 

 to the nine olfactory filaments of the female (ri) bears from sixty to 

 ninety more {ri'). 



In this and many other such cases it is not the struggle of 

 the species for existence which has so markedly augmented this dis- 

 tinctive characteristic of the male ; it is undoubtedly the struggle of 

 the males among themselves, their competition for the possession of 

 the females. In regard to decorative distinctions, the reality of a 

 rivalry in wooing and the ultimate victory of the most decorative 

 may perhaps be still doubted; but it is quite certain that, on an 

 average, the male which can smell and track best will also gain 

 possession of the females more easily than one less well equipped. 

 Exactly the same is also true of those cases in which the male dis- 



