144 BULLETIN OF THE 



haud, it measures from 5 to 10 /a in thickness. It is highly refractive, 

 and similar to chitm, although not identical in composition with that 

 substance, since it may be easily dissolved in boiling KOH. Occa- 

 sionally one notes a fibrous or lamellar structure, the layers being par- 

 allel to the surface. In most places an outer extremely thin layer may 

 be easily distinguished from the subjacent portion by its higher refract- 

 ive power. The inner surface of the cuticula is not always even and 

 clearly marked off from the hypodermis, but frequently shows a jagged 

 outline with underlying granules, which decrease rapidly in size toward 

 the muscular layer. 



On the front and upper surface of the head one finds occasional fine 

 pore canals, and in total preparations short hairs were seen, but no 

 connection between the two could be established. In the hollow pro- 

 duced by the ventral flexion of the posterior end, the cuticula displays a 

 curious peculiarity. The highly refractive outer layer remains intact, 

 but the inner layer is, as it were, bored with conical holes, into which 

 the hypodermal tissue projects. These probably represent sensory or- 

 gans, but in spite of the proximity of the anal ganglion a nervous supply 

 could not be demonstrated. 



There are present as structures of undoubted cuticular origin the 

 hairs or bristles of the lines and peculiar scales found along the posterior 

 portion of the body of the male. 



The bristles (Fig. 72) form a doiible row along the dorsal and ventral 

 lines, beginning only 0.2 mm. behind the transverse partition which cuts 

 off the anterior chamber, and extending to within 0.5 mm. of the pos- 

 terior end of the body. The two rows are only 15 to 25 /a apart, 

 and the bristles stand opposite each other (Plate II. Fig. 12) at regular 

 intervals of 10 ^. Normally they are entirely unconnected by any web 

 of tissue or mucus. They are, moreover, but lightly attached to the 

 cuticula, and hence easily broken off, so that even in the living animal 

 it is rare to find any considerable tract perfect. One can usually see the 

 scars that have been left, and apprehend from these the normal rela- 

 tion of the bristles. Each bristle is, when perfect, about 0.3 mm. long 

 and hollow, having in cross section (Fig. 13) an external diameter of 5 /a 

 and an internal one of 2 fx. The base is slightly enlarged, and rests on 

 the cuticula (Fig. 13), from which in sections it is separated by a defi- 

 nite line of demarcation. From the base the bristle tapers very grad- 

 ually to a fine point. Its cavity is simply rounded off at the base, 

 being separated from the cuticula by a thin layer; toward the point its 

 cavity gradually disappears. These structures are, then, entirely super- 



