128 LIFE-IIISTORY OF AFEICaX LIVER FI.VKE. 



forks into two jnst above the posterior sucl^er. In life the body 

 is crowded with masses of cystogenous granules contained in 

 unicelkdai cystogenous glands, which cystogenous granules 

 (" pigment " of Cawston), together with yolk, largely obscure 

 the finer details of the organisation.- 



When an infected snail is isolated in water, the cercariae 

 readily leave it, and can just be seen with the naked eye swim- 

 ming actively in the water. After a time they leave the water and 

 creep up the stems of any plant in their vicinity. Each cercaria 

 commences to extrude the cystogenous granules from its V)ody, 

 and soon casts its tail. The body then contracts into a spherical 

 mass, surrounded by a cloud of granules forming a viscid coat. 

 These gradually condense and form a thick cyst wall, which 

 hardens on exposure and contracts somewhat; they measure 

 -loOu lo 650/x in diaiueter. The encysted cercaria shows its 

 two suckers, forked gut, genital rudiments and the remains of 

 the cystogenous granules. The encysted cercariae on herbage 

 by the waterside are in favourable situations for ingestion by 

 any herbivorous animal, such as ox, sheep or buffalo. I may 

 mention that from one infected Linniaea nataJensis I have 

 obtained 1,070 perfect cysts, and several hundreds are usually 

 produced from an infected snail. 



Jiy direct experiments of feeding- herbivorous animals 

 (sheep, rabbits and guinea-pigs) and omnivorous animals (rats, 

 mice) on green barley and cabbage contaminated with cysts of 

 ('. jngmenfosa, I have succeeded in obtaining adult flukes 

 corresponding with the adult Tremaiode, Fasciola gigantica 

 of Cobboid. These adult flukes varied in size, large ones being 

 55 mm, long and up to 9 mm. broad, while small specimens 

 were about 20 mm. long. Sexually immature forms were also 

 present in my experimental animals, varying from 5 mm. to 

 10 mm. in length and in breadth from 2 mm. to -1 mm. The 

 sides of the body are nearly parallel, and the cephalic cone is 

 short. The anterior sucker is distinct, about 1 mm. in diameter; 

 the posterior sucker (acetabulum) is prominent, and in large 

 specimens reached 1"8 mm. in diameter. The genital pore is 

 situated just above the anterior margin of the acetabulum, and 

 the intromittent organ often protrudes from it. The pharynx 

 is well marked, the oesophagus short, and the numerous lateral, 

 branching intestinal caeca are directed slightlv backwards. 



The reproductive system consists of two testes, placed one 

 behind the other and much branched. Each has a vas deferens, 

 and the vasa deferentia unite anteriorh'. The ovary is rela- 

 tively small and is branched. The uterus and oviduct are 

 convoluted. Yolk glands are present and are greatly branched. 

 Tlie vitelline ducts are readily seen, and the transverse junction 

 is dilated centrally into a vitelline receptacle. A large shell 

 gland is present. The eggs are large, measuring about lT5u 

 long and 85/x broad. 



Typical experiments that I made in connection with tlie 

 elucidation of the life-history of Fasciola gigantica may be 

 briefly summarised. Thus, a rabbit was feci with green food 

 contaminated with cysts from Limnaea nataJenxis. It gradu- 

 allv became emaciated, and died (\X davs after the infective 



