356 THE DESCENT OF JIAN. 



colored than the naked skin and wattles of certain birds. In man, 

 however, when cultivated, the sense of beauty is manifestly a far 

 more complex feeling, and is associated with various intellectual 

 ideas. 



Before treating of the sexual characters with which we are here 

 more particularly concerned, I may just allude to certain differ- 

 ences between the sexes which apparently depend on differences in 

 their habits of life; for such cases, though common in the lower, 

 are rare in the higher classes. Two humming-birds belonging to 

 the genus Eustephanus, which inhabit the island of Juan Fernan- 

 dez, were long thought to be specifically distinct, but are now 

 known, as Mr. Gould informs me, to be the male and female of the 

 same species, and they differ slightly in the form of the beak. In 

 another genus of humming-birds (Grypus), the beak of the male 

 is serrated along the margin and hooked at the extremity, thus 

 differing much from that of the female. In the Neomorpha of 

 New Zealand, there is, as we have seen, a still wider difference in 

 the form of the beak in relation to the manner of feeding of the 

 two sexes. Something of the same kind has been observed with 

 the gold-finch (Carduelis elegans), for I am assured by Mr. J. 

 Jenner Weir that the birdcatchers can distinguish the males by 

 their slightly longer beaks. The flocks of males are often found 

 feeding on the seeds of the teazle (Dipsacus), which they can 

 reach with their elongated beaks, whilst the females more com- 

 monly feed on the seeds of the betony or Scrophularia. With a 

 slight difference of this kind as a foundation, we can see how the 

 beaks of the two sexes might be made to differ greatly through 

 natural selection. In some of the above cases, however, it is pos- 

 sible that the beaks of the males may have been first modified in 

 relation to their contests with other males; and that this after- 

 wards led to slightly changed habits of life. 



Law of Battle. — Almost all male birds are extremely pugnacious, 

 using their beaks, wings, and legs for fighting together. We see 

 this every spring with our robins and sparrows. The smallest of 

 all birds, namely the humming-bird, is one of the most quarrel- 

 some. Mr. Gosse" describes a battle in which a pair seized hold 

 of each other's beaks, and whirled round and round, till they al- 

 most fell to the ground; and M. Montes de Oca, in speaking of 

 another genus of humming-bird, says that two males rarely meet 

 without a fierce aerial encounter: when kept in cages "their flght- 

 "ing has mostly ended in the splitting of the tongue of one of the 

 "two, which then surely dies from being unable to feed.'" With 

 Waders, the males of the common water-hen (Gallinula chloropus) 



= Quoted by Mr. Gould, 'Introduction to the Trochilidae,' 1861, p, 29. 

 * Gould, ibid. p. 52. 



