230 Proceedings of the Royal Physical Society. 



be quite certain, since the end of the body was tightly twisted 

 into a spiral, which I found it impossible to unroll. The 

 body is covered with a chitinous cuticle, which, as in most 

 other Nematoids, is divisible into several layers. The cuticle 

 is far more strongly developed in the male, and consists of 

 (1.) an outer layer, which, in optical longitudinal section, is 

 homogeneous, but, viewed from above, shows a wavy longi- 

 tudinal striation, and readily splits into fibrils, the margins of 

 which correspond to the strife ; on the under surface of the 

 body, in the ' posterior region, where the cuticle is greatly 

 thickened, this outer layer is made up of two distinct lamellae. 

 (2.) The inner layer of the cuticle is the most important ; 

 it is homogeneous in optical longitudinal section, and the 

 upper and lower margins are crenate in outline. Figs. 2 and 

 3 represent the two layers of the cuticle in the posterior half 

 of the body in the male ; they are drawn to the same scale 

 to show the relative proportions of the thickness of the 

 cuticle on the upper and lower surfaces. Tig. 3 is taken 

 from the lower surface, and it will be noticed that the whole 

 cuticle, and especially the inner layer, is here greatly in- 

 creased in thickness, which is correlated with the presence of 

 a series of muscles attached to the cuticle, and running 

 diagonally across the body. They are found in the males of 

 many Nematoids,* and serve to connect the body wall with 

 the ductus ejaculatorius, assisting no doubt in the passage of 

 the semen down the latter. In the anterior half of the body 

 the cuticle diminishes considerably in thickness. 



In the female the cuticle is exactly similar in structure, 

 but differs in not being so strongly developed. At the 

 anterior extremity (Fig. 4) the inner layer disappears in both 

 sexes, and the outer layer alone is present. 



In most Nematoidea there are several papillae arranged round 

 the mouth, which vary in number and position in different 

 genera; they are formed by a prolongation of the cuticle, 

 and contain in many cases a delicate granular core, which 

 is probably of a nervous nature, the papillse performing the 



* Compare, e.g. figure of Mononchus given by Biitsclili (Zeit. fiir Wiss. 

 Zool. , vol. xxvi. ), wh^re the structure of chitinous cuticle is very similar to 

 that described here. 



