208 



SLUGS, FLUKES, EELWORMS, ETC. 



quarter in length, and in shape may be described as. 

 not unlike a little sole, in width about half its length, 

 flat, and largest towards the head end. At the tip of 

 its head part is placed the mouth, in the middle of a 

 small sucker, and at the point where the head joins 

 the flat body, on the lower surface, is another sucker. 

 The colour is pale brown. 



Fig. 155.— Liver Fluke in various stages: 1, Fluke, magnified, nat. 

 length somewhat more than one inch; 2, free embryo; 3, " sporo- 

 cyst " ; 4, tailed larva, or " cercaria " : all magnified. 



The eggs, which are brownish and excessively 

 minute, are passed down from the liver to the intes- 

 tines, and thus distributed with the droppings of the 

 infested animals. If the eggs fall in favourable cir- 

 cumstances for hatching (that is, warm weather on 

 wet or marshy ground, or are washed into ditches or 

 ponds), the embryo within develops in a period which 

 may be of from two or three weeks to two or three 

 months, according to temperature; then the contained 

 embryo pushes off one end of the egg-shell, and swims 

 away with great rapidity and activity. 



This embryo is described by Prof. A. P. Thomas, in 

 his minutely recorded observations from life of this 

 infestation, as being only about l-200th of an inch in 



