292 



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



The female Las a blimt tail ; the vulva probably always lies 

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

 uteri ; the eggs have a thin colourless 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 the subcutaneous 

 tissue). The presence of cei tain 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 vaiying 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 papillae ; 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 Aveak 

 spot through which the embryo escapes. 



Habitat: jS^ormally the gastric wall, usually of carnivorous 

 mammals. 



Genotype: G. spinigerum Owen, 1836. 



Note. — 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. Body completeb' clotlied with spines 6r. hisjoiduni (p. 298). 



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

 the body. 



a. The spines immediate]}^ behind the head-l)ulb comb- 

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



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



t Opinion 66 (Smithsonian Institution, Washington). 



