1896. THE STUDY OF THE GIBBON. 377 



marked characters. Its nerves,, arteries, muscles, brain, and viscera 

 have, when only one animal is examined, nothing very peculiar about 

 them ; but when a larger number is examined, the sum of the 

 Siamang's variations will be found to be strikingly different from those 

 of ordinary gibbons. 



There is still much doubt as to the number of species of gibbon. 

 An extraordinary number of species has been named, and the list of 

 synonyms is appalling — see Gray (134), Anderson (291), Blyth (295), 

 Cantor (297), and Blanford (294). Some writers have been inclined 

 to regard many, if not all, of the named species, excepting the 

 Siamang, as mere varieties of one species — Gray (134), Kohlbrugge 

 (313), and Schlegel (193). But there can be no doubt that all the 

 species named in the paragraph on distribution are quite as well 

 marked anatomically as the received species of Semnopithecus or Cerco- 

 pithecus. Dahlbom (298) was in error in ascribing to species distinctive 

 marks on the clavicles. It is true, as I have observed for myself in 

 the dissection of six specimens of H. lar and three of H. pileatus, that 

 it is impossible to draw an anatomical distinction between these 

 species, but the series dissected is too small to allow of a final conclu- 

 sion being drawn. Whether the species maintain their individuality 

 through geographical segregation, or whether, if they were to meet 

 and mix, sexual and social instincts would still maintain the 

 present arrangement of species, are matters upon which no informa- 

 tion has as yet been given. But the fact that certain of these species 

 {H. lar, H. pileatus, and H. hoolock), if not all, have voices which can be 

 distinguished, tends to show there is a physiological differentiation, 

 and the colour markings are very constant. Gray (134) and Schlegel 

 (193) give the most useful information regarding the number of 

 species and the specific characters, and to bring these lists up to date 

 I need but mention the more recent contributions on H. hainanus, 

 Thomas (322), H. leucogenys, Sclater (319^), H, entelloides, Wunderhch 

 (328), H. leticiscus (probably lav), Schmidt (317), and H. concolor, 

 Everett (300). 



REFERENCES. 



[For references numbered between 1-88, see pages 32-37; between 88-216, 

 pages 260-265 ; bettveen 216-289, pages 323-326 of this volume.] 



290. Albrecht, P. — " Sur la fossette vermienne du crane des Mammiferes." 



Bruxelles, 1884. Pamphlet, 25 pp. 



291. Anderson, John.— " Anatomical and Zoological Researches." London, 



1878. 



292. Bennett, G.— " Wanderings in New South Wales, Batavia, Pedir Coast, 



Singapore, and China." London, 1834. Vol. ii., p. 142. 



293. Bischoff, Th. Li. W. — " Beitriige zur Anatomic des Hylobates leuciscus und 



zu einer vergleichenden Anatoraie der Muskeln der Affen und des Men- 

 schen." Abh. Math.-Phys. CI. Ak. Wiss. Mi'inchen, 1870. Bd. x., Abth. iii., 

 pp. 199-297- 



294. Blanford, W. T.— " The Fauna of British India, including Ceylon and 



Burma." London and Calcutta, 1888. Mammalia, part i., pp. 5-10. 



2 D 



