160 LIFE-HISTORIES OF TREMATODES. 



spherical cyst is produced. When ingested by sheep or cattle, the 

 encysted cercaria or agamodistome develops into the adult liver 

 fluke, the structure of which is well known. 



(2) Fasciola gigantica. 



The vertebrate hosts of Fasciola gigantica are Ruminants, 

 chiefly cattle, sheep and goats. The invertebrate host I have deter- 

 mined to be the common pond snail, Limnaea natalensis. The life- 

 history of Fasciola gigantica I described last year (this Journal, 

 1920, Vol. XVII,' pp. 126-130), so that repetition here is 

 unnecessary, but it may be useful to indicate some of the differ- 

 ences between the adults of it and of F. hepatica. Thus, Fasciola 

 gigantica differs from F. hepatica in the following respects: — It 

 has a shorter cephalic cone, almost parallel sides, large acetabulum 

 which is closer to the oral sucker, an alimentary canal in which 

 the direct diverticula off the two main longitudinal stems are more 

 numerous and more backwardly directed than in F. hepatica, a 

 less conspicuous and more straggling ovary, and the posterior testis 

 more sharply delimited from the anterior one. The ova of 

 F . gigantica (measuring 150/* to 190/t by 75/* to 90/*) are also larger 

 than those of F. hepatica. 



Paramphistomes. 

 Pararn phistoni u m calicophorum . 



Owing to difficulties in obtaining literature, full identifications 

 of the Paramphistomes that I have bred in the laboratory cannot 

 be submitted here. The Amphistome herein discussed is probably 

 Paramphistomum calicophorum Fischoeder, common in the rumen 

 of cattle in South Africa. The larval stages are passed in the fresh- 

 water snail, Isidora tropica. 



The parthenita are rediae found in the liver and hermaphrodite 

 gland of Isidora tropica. The rediae are muscular and some 

 reached 3mm. in length. The cercariae are conspicuous, each 

 having an oval body measuring 400/x to 500/* long by 300/* to 400/x 

 broad, with a simple tail about as long as the body. Two pro- 

 minent, black, pigmented areas are present, which surround the 

 true eyes. The mouth and anterior sucker are well-marked, the 

 pharynx distinct. The excretory system consists of two lateral 

 tubes, which have a sinuous course, each bifurcating into two, one 

 on each side of the eye. A bifurcation also occurs just posterior 

 to the branching of the oesophagus, the branches of each side unit- 

 ing to form a continuous transverse tubule. The genital rudi- 

 ments consist of two small testicular masses with one ovarian rudi- 

 ment posterior to them. Cystogenous glands are present. 



Encystment occurs on grass or on water plants. The tail is 

 cast, and a mass of cystogenous material is poured out. Some of 

 the pigment granules are also shed. The cystogenous material 

 gradually hardens, and a more or less spherical cyst, varying from 

 400/* to 550/* in diameter is produced. These cysts fed to laboratory 

 animals developed into the large cherry -pink Amphistomes, which, 



