1922] 



H. A. Baylis and R. Daubney : Parasitic Nematodes. 



343 



probably be regarded as a pear-shaped bulb of an unusually elongate shape. It 

 measures about 032 mm. in length and 0065-009 mm. in thickness posteriorly. 

 The anterior, musclar portion of the oesophagus appears to be divided transversely near 

 its posterior end, by a kind of diaphragm, into two parts of slightly different histological 

 appearance. The nerve-ring surrounds the neck of the "bulb" (not the muscular 

 part of the oesophagus, as is usually the case), near its origin, i.e. at about 0-22 mm. 

 from the head-end of the worm. The excretory pore is situated at about 0-4 mm. 

 from the anterior end. 



In the male, the tail measures 034 mm. in length, and tapers to a very fine 

 point. There are two very unequal tubular spicules, of which the left measures 021 

 mm. in length, the right o - o8 mm. The 

 tip of the long spicule is bluntly rounded, 

 that of the short spicule more pointed. 

 There is no accessory piece. There are 

 nine pairs of caudal papillae, of which 

 four are preanal and five postanal. The 

 preanal papillae are all very close to- 

 gether, near the cloaca, and these and the 

 most anterior pair of postanal papillae are 

 very large and prominent, projecting 

 ventrally. Of the remaining postanal 

 pairs, which are smaller, one is laterally 

 situated, not far from the cloaca, and 

 the rest form a triangle, two being ventral 

 and one lateral, at about the middle of 

 the tail. 



The female has a finely tapering tail, 

 0"55-°'65 mm. long. The vulva is situat- 

 ed at about 0^45 mm. in front of the anus, and the uterus and ovary are single. The 

 latter is situated anteriorly, and is reflexed at about 12 mm. from the anterior end. 

 The worm is viviparous, the embryos being at first enclosed in large, oval, membranous 

 shells, measuring 0-275 X 0-125 mm., but subsequently hatching in utero. The 

 voluminous uterus may contain at one time some 15 to 20 eggs containing embryos 

 in various stages of development, and about four or five free embryos. The latter 

 are about 1 mm. long, or roughly a quarter of the length of the parent. 



.The systematic position of this species is somewhat doubtful, but we are inclined to regard it as a 

 member of the usually free-living family Anguiilulidae that has recently taken to a parasitic mode of 

 life. It does not show the specialization of the female genital apparatus which usually takes place in 

 true internal parasites. One of us (Baylis (1915)) has described two semi-parasitic species apparently 

 belonging to the genus Monhystera, and it is to this genus that the present form seems to approach 

 most closely in its general anatomy. 



Fig. 75. — Monhysterides piscicola. 

 of male; lateral view. 



I., left spicule; r., right spicule. 



Posterior end 



