402 W. G. EIDEWOOD. 



lu Choice pus, as in Brady pus, the hairs are very thin 

 at their basal ends (60 fi). The fluting'S of the surface die 

 away on the basal sixth of the hair, and here the structure is 

 that of a normal nou-medullate hair (figs. 10 and 11). The 

 cortex is not marked by the deeply staining branched tubes, 

 but is rendered slightly granular by the presence of a number 

 of fiue air spaces, some spherical and scattered, some sphe- 

 rical and arranged in series of five or six, like strings of 

 beads, and some fusiform, as though formed by the coales- 

 cence of such series of smaller cavities. The cuticle is thin 

 and distinctly imbricate. 



There are in Choice pus no fine hairs to constitute a 

 proper under-fur, and Welcker has remarked (17, p. 70), 

 " Der Gegensatz von St ichelhaaren und Wollhaaren fehlt bei 

 Cholcepus;" but de Meijere (9, p. 361) has described some 

 flattened, stiff, and slightly curved hairs, much shorter than 

 the ordinary hairs, and possessed of large medullary cells, 

 surrounded by a very thin cortical layer. These hairs I have 

 searched for in vaiu. 



Myrmecophaga jubata. 



The hairs of the great ant-eater are much flattened, and 

 resemble a ribbon which is thinner in the middle than toward 

 its edges. The actual measurements are — breadth 400 ,u, 

 thickness in the middle llOju, thickness near the edge 170 ju. 

 The cuticle is thin for the size of the hair, and exhibits, 

 rather indistinctly, the usual imbricate or serrate appearance, 

 according as a surface view or an optical section is taken. 

 The cortex is full of air spaces (fig. 14), which are provided 

 with a deeply staining lining after the manner of the branch- 

 ing tubes which permeate the cortex of the Choice pus hair. 

 These spaces, however, can hardly be regarded as a diffused 

 medulla, since a true medullary region is here differentiated ; 

 and the suggestion made to this effect in the case of Cho- 

 Icepus tlius receives by analogy a partial refutation. When 

 the hair is examined from the side the cortical vacuoles are 



