562 



TREMATODA 



Watsonius Stiles and Goldberger, 1910. 



Definition. — Cladorchiinse without genital sucker, with lobate 

 or lobulate testes, without cirrus pouch, and with each oral invagina- 

 tion single. 



Species. — Wqtsonius watsoni {Conyngham, 1904) Stiles and Gold- 

 berger, 1910. 



Watsonius watsoni (Conyngham, 1904) Stiles and Goldberger, 1910 . 



Synonyms. — Cladorchis watsoni (Conyngham, 1904), Amphistomum 

 watsoni (Conyngham, igo/\.) , Paramphistomum watsoni (Conyngham, 

 1904). 



Definition. — Watsonius with the characters of the genus. 

 History. — W atsonius watsoni was first discovered in the duodenum 

 and upper part of the jejunum of a negro who had come from 



Adamawa, in late German West 

 Africa, to Northern Nigeria . Since 

 its discovery it has been reported 

 near Lake Chad. The type was 

 first described by Conyngham, 

 later by Shipley, and in 1910 by 

 Stiles and Goldberger. 



Morphology, — The parasite is red- 

 dish-yellow when fresh, 8 to lo milh- 

 metres in length by 4 to 5 millimetres 

 in breadth. In shape it is oval or 

 pyriform. The ventral sucker is large 

 and situated posteriorly and subter- 

 minally, while the oral sucker is so 

 small as to be hardly worthy of being 

 considered a true sucker. It has a 

 pair of lateral caudal irregularly 

 globular suctional pouches. The 

 pharynx is spherical, with two lateral 

 diverticula, called the ' pharnygeal 

 pouches.' The oesophagus divides 

 into two long intestinal caeca about 

 the level of the junction of the anterior 

 third with the posterior two-thirds of 

 the body, and is here surrounded by a 

 sphincter muscle. The excretory pore 

 opens slightly to the left of the middle 

 line dorsal to the posterior sucker. 

 The excretory vesicle is relatively 

 small, and lies over that sucker. The 

 genital papilla is situated in the mid- 

 ventral line, about the junction of the 

 anterior quarter with the posterior three-quarters of the body, and on it open 

 the canal of the cirrus and the metatrema. The testes, which lie one behind 

 the other, are deeply lobulated. The vas deferens runs into a vesicula semi- 

 nalis, which opens into the cirrus canal, but has no true cirrus pouch. 



The ovary lies close behind the testes, and rather to the right of the body. 

 The ovarian duct curves backwards, and is almost at once surrounded by 

 the shell gland, when it may be called the ' ootype,' which just behind the 

 shell gland receives the vitellarian duct and the inner end of Laurer's canal. 

 The uterus, full of eggs, coils over the testes and runs as far forwards as their 



Fig. 212. — Watsonius watsoni. 

 (After Shipley; emended by Leiper.) 

 a, Schematic; b, natural size. 



