4 
Larval Trematofles 
A Larval Maritrema encysted in Ligia oceanica. 
Specimens of Ligia oceanica were sent to me in October 1912 by 
Mr Elmhirst from Millport in which species he had found an encysted 
Trematode occurring abundantly in the genital ducts of both male and 
female. The Ligiae live just above high water mark in the tidal drift 
below the laboratory, generally under stones. 
In both oviducts and vasa deferentia the cysts were scattered about, 
sometimes also occurring in the other organs, more particularly in the 
muscles. The cysts were either colourless or a bright yellowish brown, 
the latter probably being older, and in.side each cyst was curled up 
a larval Trematode which undoubtedly is a species of the genus 
Maritrema Nicoll. 
The cysts (Plate I, tig. 4) are oval and measure 0‘36-045 mm. 
by 0’24-0'32 mm. and with a thick cell wall measuring 0'02 mm. in 
thickness. Each cyst has very much the appearance of a Trematode 
egg. I have called this worm Cercaria ligiae sp. inq. 
Cercaria ligiae. Inside the cyst the curled-up larva is visible 
through the transparent wall. The oral and ventral suckers, alimentary 
canal and excretory vesicle are easily made out. The head and 
posterior end are folded in towards each other in.the cyst. During the 
encysted stage the excretory organs of the posterior end have a peculiar 
structure. The vesicle is much dilated and full of conspicuously 
refractive granules. If by any chance the cyst is ruptured accidentally 
these granules always come out quickly from the excretory pore which 
is at the extreme posterior end. The granules are irregular in shape 
and perfectly clear. 
The most successful way to get the worm out of the cyst is to leave 
it in normal salt solution over night. The larval worm will have 
emerged by the next morning and will be still living and can be 
examined alive. The refractive granules of the excretory system how¬ 
ever will have all disappeared. 
The whole body (Plate I, figs. 2 and 3), is quite colourless and 
transparent, very much fiattened dorso-ventrally and with the sides 
having a tendency to fold over ventrally. The first two-thirds are 
covered with small spines and scattered about at much greater intervals 
are conspicuous unicellular glands. It is more or less tongue-shaped 
with the anterior end slightly more pointed than the posterior and 
usually narrow in the middle region. When contracted it is more oval. 
The length of the worm is 060 mm.-0'66 mm. and the breadth 
