292 MR. H. A. BAYLIS AND LT.-COL. CLAYTON LANE ON 



The female has a blunt tail ; the vulva probably always lies 

 behind the middle of the body; the vagina is long ; there are two 

 uteri ; the eggs have a thin coloui-less shell, marked by a very 

 fine external stippling, and have at one pole an appearance 

 as of a watch-glass-shaped cap due to a thinning of the shell 

 combined with a recession of the shell-membrane, and providing 

 a means of exit for the embryo. It has, however, sometimes 

 been described as a polar thickening of the shell (Schneider, 

 1866, p. 98; v. Linstow, 1893, p. 207). 



The genus {vide Table VIII., p. 304) has a wide distribution 

 in a number of carnivorous hosts. Its normal habitat is clearly 

 the wall of the stomach. The genotype acquires an added 

 interest in that it has been found in man (in tlie subcutaneous 

 tissue). The presence of certain species in the lumen of the gut 

 we attribute to their having been parasitic in some host which 

 was devoured by the animals from which they were actually 

 recorded. Regarding one record of a Gnathostoma from the 

 colon judgment must be suspended {vide p. 305). 



Generic Diagnosis. 



Gnathostoma* Owen. 



Gnathostominse : head-bulb armed , with simple hooks, the 

 ballonets giving no external evidence of their presence ; body 

 armed with cuticular spines, anteriorly scale-like with the free 

 edges incised into points varying in number and shape, more 

 posteriorly becoming less subdivided and finally appearing as 

 simple spines, which either continue as such to the posterior end 

 or disappear, leaving the hinder part of the body unarmed; the 

 male with unequal spicules and four pairs of large lateral and 

 two pairs of small ventral caudal papillfe ; vulva behind the middle 

 of the body ; vagina long ; uteri two in number ; ovum with thin 

 colourless shell, a marked thinning at one pole causing a weak 

 spot through which the embryo escapes. 



Habitat: Normally the gastric wall, usually of carnivorous 

 mammals. 



Genotype: G. sinnigerum Owen, 1836. 



XoTE.— The name Gnathostoma has been placed on the official 

 list of generic names by the International Commission on 

 Zoological Nomenclature f. 



Key to Species of Gnathostoma. 



A. Bod}' completely clothed with spines G. hls^pidum (p. 298). 



B. Spines clothe only the anterior half or two-thirds of 



the bodj'. 

 a. The spines imniediatelj' behind the head-ljulb comb- 

 like, having four points of about equal length G.spiiiifferuin (p. 293). 



* For measurements, see Table VII., p. 302. 



f Opinion 66 (Smithsonian Institution, Wiishington). 



