Chap. VI.] AFFINITIES AND GENEALOGY. 185 



radiates from a point on the crown, with a parting down 

 the middle, as in man. It is commonly said that the fore- 

 head gives to man his noble and intellectual appearance ; 

 but the thick hair on the head of the Bonnet monkey ter- 

 minates abruptly downward, and is succeeded by such 

 short and fine hair, or down, that at a little distance the. 

 forehead, with the exception of the eyebrows, appears 

 quite naked. It has been erroneously asserted that eye- 

 brows are not present in any monkey. In the species just 

 named the degree of nakedness of the forehead differs in 

 different individuals, and Eschricht states 7 that in our 

 children the limit between the hairy scalp and the naked 

 forehead is sometimes not well defined ; so that here we 

 seem to have a trifling case of reversion to a progenitor, 

 in whom the forehead had not as yet become quite naked. 

 It is well known that the hair on our arms tends to 

 converge from above and below to a point at the elbow. 

 This curious arrangement, so unlike that in most of the 

 lower mammals, is common to the gorilla, chimpanzee, 

 orang, some species of Hylobates, and even to some few 

 American monkeys. But in Hylobates agilis the hair 

 on the forearm is directed downward or toward the wrist 

 in the ordinary manner ; and in H. lar it is nearly erect, 

 with only a very slight forward inclination ; so that in 

 this latter species it is in a transitional state. It can 

 hardly be doubted that with most mammals the thickness 

 of the hair and its direction on the back is adapted to 

 throw off the rain ; even the transverse hairs on the fore- 

 legs of a dog may serve for this end when he is coiled up 

 asleep. Mr. Wallace remarks that the convergence of the 

 hair toward the elbow on the arms of the orang (whose 

 habits he has so carefully studied) serves to throw off the 

 rain, when, as is tMe custom of this animal, the arms are 



7 " Ueber die Richtung der Haare," etc., Muller's ' Archiv fur Anat 

 and Phys.' 1837, s. 51. 

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