442 Second Report of Experiments of the 
Experiments with Limn^us Teuncatulus. 
On obtaining the snails I had so long been searching for, I 
exposed a number to infection bj placing fluke-eggs and free 
fluke-embryos in the vessel with them. The snails were speedily 
found to have afforded a suitable place for the further develop- 
ment of the embryos, and of those examined up to the present 
time all have proved to be infected, often containing as many 
as eighty embryos. Indeed, the infection was too successful, for 
about the tenth day many of the snails began to sink and die, 
simply because they were exhausted by the excessive number ot 
parasites, so that at the end of the fourth week I had only two 
left alive out of the eighty that had been infected. 
Fig. 1. 
Egg of the Liver-fluke examined shortly after it was taken frcim the liver of a sheep. At one end of 
the shell may be seen the line marking off the lid, and a little below, the embryo in a very 
early stage of development, and surrounded by the secondary yolk-spheres, only three of 
which have been filled up. Magnified 6S0 diameters. 
Before describing the changes which the embryo passes 
through, I will briefly mention its more important characters, 
referring to my former paper for fuller details. The free 
embryo of the liver-fluke has a bluntly conical form (see Fig. 2). 
The broad end is directed forwards, and in its centre is a head- 
papilla which is ordinarily short and blunt, but when employed 
for its purpose as a boring-organ becomes long and pointed (see 
rig.). The whole surface of the body, except this head-papilla, 
is covered with a layer of flat cells, arranged usually in five rings 
around the body, and carrying long cilia, by means of which 
the animal swims rapidly through the water. Beneath these 
outer ectoderm cells is a layer of granular tissue, which contaihs 
transverse and longitudinal muscle-fibres. The longitudinal are 
more feebly developed than the transverse, and are only seen 
