BIRDS 145 



observation that these birds peck at each other when fight- 

 ing, or that their habits in one way or another involve a 

 special mechanical irritation of the skin about the bill. But I 

 feel strongly convinced that the modification of the skin in 

 that region, which occurs in the males of all the species, 

 corresponds to, and is due to, some such irritation ; and 

 further, that it will some day be proved that the special 

 excrescence or modification in each species has been developed 

 in the particular point or area to which the irritation is 

 habitually applied. The most probable conjecture is that the 

 males fight a great deal, and that in combat they seize their 

 adversaries by the skin at the base of the beak, the attack 

 being directed to the chin or the forehead according to the 

 species. If this were true it would be an excellent illustration 

 of the superiority of the Lamarckian explanation to that of 

 sexual selection, for the caruncles would serve rather as an 

 advantage to the adversary who seized them with his beak, 

 than to the bird that possessed them. 



In all the species of ChasmorJiynchus the male differs from 

 the female in structure, colour, and voice. C. nudicollis and 

 C. niveus have pure white plumage, C. tricarunculatus has a 

 chestnut body with white head and neck, C. variegatus has a 

 white body with brown head and black wings. The females 

 of all four species are closely similar, and Mr. P. L. Sclater l 

 has discussed the divergence of the four species on the 

 selection hypothesis. With regard to the colour, I have only 

 to remark that if we attribute it to sexual selection we have 

 to suppose that the hens have in one case preferred one 

 colour, in another another, and that the divergence of the 

 males is due to a variety of taste in females originally of one 

 species. 



The Umbrella-bird, Cephalopterus ornatus, belongs to the 

 same family, and lives likewise in South America. This 



1 Intellectual Observer, 1867. 

 10 



