LIFE-ITISTOKY OF AVIUCAX LIVKR FLUKE. 127 



A^ Fasciola (jifjanfica i^ widely clistrilaited in South 

 Africa, a summary of its principal features and life-liistory 

 is now given. 



Fasciola (jiijanfica (("obbold, 185*]) is the large, narrow 

 liver fluke of cattle and sheep in South Africa. It was also 

 described under the apt name of F. angasta by Railliet in 

 18!)."). This fluke has been reported fronr certain big" game, 

 namely, giraffes, zebras and buffaloes. It has also been found 

 once in man. The larval stages of the fluke I have found in 

 the common pond snail, Liinuiiea nafaleiisis, and by experi- 

 mental work, using laboratory-bred rats, rabbits, <;uinea-i)igs 

 and sheep, I have been able to determine the entire life-history. 

 Also, by exposing laboratory-bred, and therefore uninfected, 

 Liinnaea natal en sis to tlie larvae (miracidia) issuing from the 

 eggs of F. ijiijanfica . the earliest stages in the snail have been 

 obtained. 



In 191.), Dr. Cawstou described a distome cercaria from 

 Lininaea natalensis in the following words: " The other 

 encysting cercaria possesses a terminal oral and a median 

 ventral sucker. Xo eyespots could be detected. The head 

 of the cercaria is heavily pigmented, as are also the rediae 

 in which these cercariae are produced. These lediae are 

 three-eighths of an iindi in length, and whiten the liver sub- 

 stance of infected snails. The cercaria itself is fully a milli- 

 metre in total length. The rediae possess a well-defined oral 

 sucker and gut distended with particles of food. Towards the 

 posterior end of the rediae on the left side is a poorly developed 

 locomotor appendage." Cawston named the cercariae " C . pig- 

 inentosa in view of their pigmented heads." Unfortunately, 

 the description is insuflicient to enable the certain determina- 

 tion of the (.-ercaria, but I believe that the organism I used, 

 which developed into Fasciola gigautica, was the (' . pigmentosa 

 of Cawston. This may jjossibly be the same as ('. ohscara of 

 Sonsino. 



xln outline of the structure and life-history of Fasciola 

 f/igantica, as I have observed it, is presented here. 



When the liver of a Liinnaea natalensis infested with this 

 juirasite is examined, it appears to be streaked M'ith white 

 threads, which sometimes show orange to blaidv markings. 

 These threads are the rediae of F. gigantica, the intestines 

 of which contain orange to black contents. The rediae vary 

 in size with the season and the particular time of reproductive 

 activity of tlie fluke in the snail. The largest specimens were 

 about 12 mm. long, but this was quite excei)tional, the usual 

 size being from 1"5 to 2 mm. long. Daughter rediae appear 

 to be formed only towards the end of the life of the parent 

 redia. The parent redia produces several cercariae, Avliich are 

 active organisms, and A'ary in apjiearance according to their 

 degree of activity. The body of a cercaria measures about fiiW'i. 

 when fully extended, but when contracted it apiiears rounder, 

 and may measure only 250m. The tail is simple, and varies 

 in length from 159/i to 200/y.. The anterior sucker is fairly 

 pi'ominent, and the posterioi' one easily seen. The intestine 



