Introduction: Variation. 55 



temperament in individuals; some are bold and fierce, others more gentle; some 

 more clever, others more stupid; some trustful, others shy; and so on. A marked 

 "individuality" in birds may sometimes be noticed in their choice of their feeding 

 grounds and nesting spots. 



Monstrosities. — Cases of exceptional individual variation, infraction of the 

 rule of bilateral symmetry') etc., have not fallen under our observation among 

 Celebesian birds. There is a tame Duck with webless toes in the Sarasin Col- 

 lection from North Celebes. 



Albinism, Melanism, etc. — Among genera occurring in Celebes albinism, 

 partial or complete, seems to be most frequent in the Coucals, Centropiis and 

 Centrococcyx. The Hornbill, Cranorrhinus sometimes displays white spots on the 

 tail, but this may be a partial reversion to a form with a white band across 

 the rectrices, as seen in some allied Hornbills. Cases of albinism are so common 

 in the Heron, Demiegretta sacra, that this species may be rightly termed dimorjihic. 

 A further advance of albinism is seen in species which are now always white, 

 such as certain Herons and Swans, for it seems certain that these birds were 

 at one time coloured species. 



According to the observations of Mr. K. G. Henke (see, besides, Z. ges. Orn. 

 1886 HI, 268), albinism, when partial, does not conform to the ri;le of bilateral 

 symmetry. 



Partial melanism occurs in a highly variable degree in the large Talaut 

 Oriole, Oriolus melanisticiis, which appears to be developing into a species with 

 a black upper surface. The Bittern, Xanthocnus melaenus (Salvad.) may ulti- 

 mately prove to represent a case of frequent melanism in X. flavicollis. Per- 

 manently black species among Celebesian birds are Ictinaetus malayensis (when 

 adult), Surnicidus musschenhroeki, Eudj/namis (males), Wiabdotorrhinus exaratiis and 

 Cranorrhinus cassidix (females), Dicrwrus, Corvus, Limnocorax. 



Examples of individual xanthochroism in Trichoglossus ornatus have been 

 mentioned by Briiggemann, Meyer, and Guillemard among Celebesian birds 

 (see text, p. 121). The species of Cacatiia and Myristicivora are probably permanently 

 xanthochroistic forms. The sulphur tint of the plumage of the former in life'-) 

 is due to the absence of the pigment fuscin, the colour parrot-green being 

 caused by the yellow pigment psittaco-fulvin lying on the fuscin (see, Meyer, 

 Sitzb. Ak. Wiss. Berlin 1882, 518/; and the similar tint in the Nutmeg Pigeons 

 is probably caused in the same manner, very possibly by the same pigment. 



Dichromatism. — The phenomenon of dimorphism seems to be classifiable 

 under Individual Variation, although there are cases where it appears to mark 

 the commencement of the evolution of a new species. The best illustration of 



') See below p. as. 



-] It fades through exposure to the light iu course of time in skins and stuffed examples, leaving the 

 plumage white. 



