24 



of the males die and are swept away in the stools, before the 

 presence of the parasites is revealed by their characteristic 

 symptoms. This accounts for the fact that the earlier 

 naturalists were ignorant of their existence, and believed 

 the worm to be either a-sexual or hermaphrodite. 



External Appearance. 



General characters : Like " short pieces of fine white 

 thread." The body is cylindrical, and shows no signs of 

 segmentation. Head somewhat pointed, in both sexes. 

 Tail in the male, blunt or truncated, usually spirally coiled, 

 and the extremity capable of forming a sucking surface ; 

 in the female, the tail tapers to a sharp point, whence is 

 derived the name, oxyuris, i.e., pointed tail. 



Colour : Males and young females, pale silver grey ; 

 mature females, opaque chalky white, the colour being due 

 to the distension of the body-cavity by pale-coloured eggs 1 . 



Mouth : At anterior end, sometimes triangular, sometimes 

 round, according to its degree of contraction, and furnished 

 with three lips. Two cuticular sacs in this region are dis- 

 tended with clear fluid, and have an appearance which is 

 described as " wing-shaped 2 /' 



The anus : In the female, at the base of the tail ; in the 

 male, the anus, or cloaca, is at the extreme end of the tail. In 

 the latter, the cloaca contains a single spicule, the male organ. 



The vagina opens on the ventral aspect of the female, 

 slightly in front of the middle of the animal's length. 



Skin. 



The skin consists of epidermis and corium. The former 

 is a delicate, structureless membrane, with no cells. The 

 corium is densely fibrous, and marked by four longitudinal 

 seams. During motion it is thrown into broad folds. Trans- 

 verse striae are also well marked during movement, and the 



1 "If* an ordinary full-grown 2 The appendages of the head 



female worm be submitted to micro- are sacs of cuticle, probably dis- 



scopic examination, even the em- tended by endosmosis : " . . . 



ployment of the one-inch achroma- a tete ailee ou montrant deux 



tic objective glass will reveal the renflements lateraux vesiculeux du 



presence of a multitude of eggs tegument (produits par vui effet 



internally." (CoBBOLD, T. S., op. d'endosmose ?)." (DUJARDIN, M. F., 



cit., p. 81.) op. cit., p. 138.) 



