CHAP. IV] THE GENERAL ANATOMY OF THE LEMUROIDEA 67 



hairs on the head may be noted first. In the Lemurs, the hairs 

 are directed from the brows backwards (cranio-caudally) ; but they 

 encounter an opposing stream just before they have attained the 

 region above the top of the ear (Fig. 35). This opposing stream 

 ascends from twin centres (Fig. 36) placed symmetrically on each 

 side of the nape of the neck. 



A spiral centre of dispersion on each side of the abdomen is 

 another characteristic feature of the Lemurine hair. At the elbow 

 (Fig. 37), the convergence of hairs from the arm and forearm 

 respectively is a character common to the Lemurs and many other 

 mammals, including Man himself. 



Specimens of Lemurs 1 in the Cambridge Anatomical Collection 

 shew hairs distributed on the back (dorsal surface) of each finger 

 and toe : in the pollex and hallux the distal phalanx is not thus 

 covered : the hairs on the other digits extend to the nails. 



In conclusion, it may be remarked that the hairs are commonly 

 implanted in groups consisting of more than three hairs 2 . This 

 arrangement is of interest in relation to that of the hairs in 

 certain scale-covered animals, supposed to indicate the descent of 

 mammals from scale-clad ancestors. 



C. The skin (in specimens doubtfully referred to L. mongoz) 

 is of a dull slate-grey colour where exposed as near the nose, and 

 on the hands and feet. 



Professor Schwalbe appeals to the details of muscular development, or to variations 

 in the proportions of different parts, which are only indirectly affected by the 

 external agents suggested above. And such indirect influence is here held to be 

 more probable than the alternative. In particular, it is thought that Professor 

 Schwalbe is especially helpful when he calls attention to the necessity for con- 

 sidering the precise form of the surface to be provided with a hairy covering. This 

 aspect of the problem will fall within the province of a geometrical analysis such 

 as has been applied to the cutaneous surfaces of the palms and soles by Kolossof 

 and Paukul (Morphologisches Jahrbuch, xxxv. 1906). These authors point out the 

 existence of certain " neutral points " in any area of skin which is liable to changes 

 in its surface form. During such changes, the neutral points escape the effects of 

 tension or pressure necessarily felt by other points on the surface. It may well be 

 the case that such points are suitable for the hair-bulbs, and that the grouping of 

 the hairs is determined by their relative positions (v. infra in connection with 

 hair-tracts). 



1 The species is undetermined, but is probably L. mongoz. 



2 Cf. Meijere, Morphologisches Jahrbuch, Band xxi. 1894. 



5—2 



