162 LIFE-HISTORIES OF TREMATODES. 



The sporocysts are small, thin and colourless. Many of those 

 seen were about 200/t to 300^i long, and 90/* to 15CV wide. They 

 are nonmotile, but when cercariae are present and writhing about 

 within, the sporocyst moves backwards and forwards. The cercariae 

 seem to mature two at a time and emerge from any part of the 

 sporocyst. It is noteworthy that, in the majority of Echinostomes , 

 the cercariae are produced from rediae. So far, in the relatively 

 small amount of material at my disposal I have not found rediae 

 and only small numbers of sporocysts. 



The cercariae are very active and simple tailed. The anterior 

 pharyngeal region is protrusible. The acetabulum is large and 

 active. The posterior end of the body is prolonged downwards 

 laterally forming small caudal pockets around the tail, which organ 

 narrows somewhat abruptly and then swells out near the end, pro- 

 ducing a pegtop-like appearance. The excretory tubule is fairly 

 straight in the tail, but dilates somewhat in the "pegtop" area. 



Encystment occurs, both in the liver of the snail itself, on the 

 edge of the mantle and on the outside shell of the snail. The 

 cysts are from 125/* to 150 in diameter. The cyst wall is thick, 

 transparent and firm. The body of the agamodistome when fully 

 developed is beset with cuticular spines, and two rows of large 

 spines are on the collar which is set on a collar ridge. Rudiments 

 of the genitalia are more obvious than in the unencysted cercariae. 



The adult flukes measure from 5mm. to 10mm. long, their 

 breadth varying from l-5mm. to 2mm. The anterior or oral sucker 

 is fairly large, the acetabulum large, conical and powerful. The 

 pharynx is muscular and often is thrust through the mouth during 

 active movements. The oesophagus is of medium length, branching 

 into two intestinal caeca immediately above the acetabulum. The 

 ovary is simple, there is a large shell gland, and the coiled uterus 

 is usually crowded with brownish ova. Numerous small vitelline 

 glands are present near the margin of the body, extending from 

 the posterior end of the body to the rim of the acetabulum, the 

 transverse duct sloping slightly anteriorly before uniting with the 

 shell gland. The testes are two in number, one immediately behind 

 the other. The posterior testis is expanded somewhat and in some 

 specimens appears somewhat trilobed. A large excretory vesicle 

 is present. 



For purposes of reference the name Echinostomum fulicae 

 with characters outlined in the preceding is proposed for this fluke. 

 As far as I can ascertain, after consulting such Echinostome litera- 

 ture as the monograph of Odhner (1910), the fluke herein brieflv 

 described does not agree in morphology with any of those with 

 which I have been able to compare it. 



(2) Echinostomum xenopi. 



The life-history of this fluke is set forth in my paper in" the 

 "Medical Journal of South Africa," Vol. XV, pp. 128-133, and 

 need be only briefly outlined here. The larval flukes are parasites 

 of Physopsis africana. The rediae vary greatly in size, but many 

 are about l-5mm. long. They contain orange chromatophores and 



