M. V. Lebour 
437 
could be seen which were just breakiug away. In the autumn and 
winter all traces of the sporocysts had gone and the cysts were quite 
free. 
The cyst is spherical, 0'08 mm. across, quite ti’ansparent and colour¬ 
less. The cercaria when pressed out of the cyst is 0’2 mm. long and 
very broad at the base. It is covered all over with small spines, more 
conspicuous near the head which appears very rough. Oral sucker 
0'026 mm. across, ventral sucker about the same size occurring about 
three parts of the way down the body. Prepharynx very much shorter, 
long oesophagus, intestinal caeca reaching to about the level of the 
posterior border of the ventral sucker. The two lateral excretory 
canals unite behind the pharynx. 
Nothing further is known of the life-history. It is very likely a 
species of Maritrema and perhaps the habit of encysting in the sporocyst 
may distinguish this genus from Spelotrema. 
(d) Stumpy-tailed Cercariae. 
Three different species belonging to this very well-marked gi-oup 
occur in Britain, one of which I have already recorded (1906, p. 5) e.g. 
Cercaria linearis Lespes, one which I now record as new to Britain 
C. hrachyura (Lespes) and one new species. All are characterised by 
their very short stumpy tails which are incapable of independent 
movement and probably serve to attach the animal (acting as a sucker) 
whilst it is looking out for its intermediate host. The oral sucker is 
armed with a stylet and the stylet glands are conspicuous. The suckers 
are almost equal, the ventral sucker situated near the posterior end. 
The excretory vesicle is extremely thick-walled; the large lining cells 
making it appear almost solid. 
Cercaria linearis Lespes (1857, p. 113). 
(PI. XXVII, figs. 12, 13.) 
This cercaria occurs in Littorina littorea from Budle Bay and also 
from Millport. It is rare however, only being found in one specimen 
out of 190 examined from Budle and in one out of about the same 
number from Millport, both in July. 
The sausage-shaped sporocysts are very inert and occupy the kidney 
and mantle cavity spreading also into most of the other organs. They 
measure 2'6 mm. in length and are a brilliant orange, the colour being 
due to granular masses scattered throughout the sporocyst. The 
