148 



Platy helminths. 



of a pharynx and a simple sao-shaped gut. The redias break thi-ough the 

 maternal body-wall and wander about in the Snail, consuming its liver. In 

 these, eggs are again formed, which become "cere arise," with a branched 

 alimentai-y canal and a caudal appendage. They escape through an opening 

 in the maternal tissues, and later from the body of the Snail also. The cercaria 

 swims actively for some time in the water, then it attaches itself to some plant, 

 loses its tail, and secretes a mucous- substance which hardens into a cyst round 

 the body. If it be swallowed with the food by a Sheep or an Ox, the capsule 



Fig. 104. Distomum hepaticum. 1 newly hatched larva, t boringf papilla, o e-o. 

 2 the same (young sporocyst of the first generation), after it has entered the snail and 

 lost its ciliated coat, h ovnm. 3 adnlt sporocyst of the first generation. 4 redia of the 

 second generation. / Limb-like projection, Tij — Tij eeroarise developing within the redia, 

 le oercaria-embryo, m month, ia gut, v genital aperture. 5 cercaria, Ku glands, whose 

 secretion forms the capsule. Si — 52 suckers, ta gut. All the figures are eiilarged. — After 

 Thomas ; 4 slightly altered. 



is dissolved by the gastric juice, and the young Trematode wanders into the 

 liver, where it attains sexual maturity (the hermaphrodite generation). 

 Encysted Liver-flukes are found not only on water, but also on land plants, for 

 the Snail frequently leaves the water and wanders about in the adjacent 

 meadows. 



2. Lewcochloridiwm paradoxum is a parthenogenetic trematode, parasitic in 

 Suceinea amphibia, a Gastropod inhabiting damp places. This peculiar form has 

 the appearance of a sac with numerous branches, some of which attain a very 

 great development, forming thick, brightly coloured rods, which push their way 

 into the tentacles of the Snail, and expand them enormously. Different insect- 

 eating Birds tear the " rods " out of the Snail, which may go on living with a new 

 branch of the Leucochloridiimi in its tentacle. In the digestive tract of these 



