Mr F. E. Beddard on a Neio Nematoid Worm. 231 



function of tactile organs. In the species that I am descrilj- 

 ing here there is only one mouth papilla, which is curved 

 outwards and downwards, its general direction being nearly 

 at right angles to the long axis of the body (Fig. 4). There 

 is, so far as I am aware, no genus of Nematoids in which 

 the mouth papillae are reduced to a single one, though there 

 are many genera in which they seem to have disappeared 

 altogether ; the only thing that suggests itself as at all com- 

 parable is the single boring papilla (" bohrzahn ") found in 

 the young of Ascaris and Cucullanus* If this comparison 

 be just, we have here an interesting survival in the sexually 

 mature worm of a larval structure. 



The alimentary canal consists of three divisions (1.) oeso- 

 phagus ; (2.) intestine ; (3.) rectum. 



The oesophagus occupies about one-tenth of the whole 

 length of the alimentary canal, and appears to be covered 

 externally, and lined internally by a thin chitinous layer. 

 The opening of the mouth is not exactly terminal, it is very 

 slightly ventral in position. A chitinous ring is continuous, 

 save for a small space, round the whole circumference of the 

 aperture. 



The cesoj)hagus is cellular in structure, not muscular, the 

 constituent cells being easily distinguishable, especially in 

 the hinder portion. The free-living forms very frequently 

 possess a cellular oesophagus ; according to Dr Bastian,-)- this 

 is the case in about one-half of the known forms, while 

 among the parasitic genera a muscular structure is the rule, 

 but is not found in TricJwsoma, Trichocephahis, and Trichina. 

 An Oxyuris also is figured by M. Osman Galeb,J with a dis- 

 tinctly cellular oesophagus; but the number of parasitic forms 

 which are thus characterised is not large, and Blitschli, who 

 has of late years published a great many memoirs on the 

 Nematoidea, more especially the free - swimming forms, 

 remarks :§ — "One thing appears frequently in the histological 

 structure of the oesophagus of the free-living forms which is 



* Leuckart, Die menscliliclien Parasiten, A'ol. II. ; Liiistow, Arch, fiir 

 Natiirg., 1878. 



t Phil. Trans., 1866. X Arch, de Zool. Exp., 1878. 



§ Abh. Senk. Naturf. Gesell., Frankf., bd. ix., p. 248. 



