nr.) 
, has a very short and broad tail, its oral and ventral suckers are 
[most of the same size— the former having one large spine at its 
aterior end— and there are four ducts by this sucker belonging 
> the glands or ' stacheldriisen,' the salivary apparatus of Lespes. 
could not see the four large cells described by Lespes belonging 
> these. At the posterior end just above the tail there is a large 
tcretory sac. 
A specimen of Littorina rudis from Holy Island opposite the 
inssel scaup contained sporocysts of a trematode in grape-like 
lasses in the liver. These were full of tail- less cercaria? (sec Plate 
[., fig V.) This was in the beginning of May. The pale-yellow 
)imd sporocysts are each about 1 mm. in diameter and are crowded 
ith numerous cercari.e curiously doubled up. The way these lie 
1 the sporocysts is worth noting, the head end being nearly always 
jubled in, giving the worm the appearance of a pouch. When ex- 
•nded the cercaria measures 0.25 mm. in length, it is pear shaped, 
ad the body is covered with small spines for the first two thirds of 
fits length. The oral sucker leads into an (esophagus which in 
lira leads into a pharynx from which a long inirrow intestine runs 
DWn for not quite two thirds of the length of the body and bif'ur- 
ites into two short lobes. The ventral sucker is just between these, 
liis cercaria is evidently the same species as the encysted form 
hich Mcintosh found in the common green crab, Oncinus vnrnas 
Journal of Microscopical Science, 1866). Brandes (Archiv £ 
fttiirgesch., 1888, Bd. 1.) regarded this as the encysted form of 
Hsloiinim chni/oime which lie describes from the Dunlin. Mr. 
icoll ((,/*. cit.) is of the opinion that it is just as likely to be the 
icysted form of Distumwn similis, Jagerskiold, which species he has 
iscovered in the Herring Gull at St. Andrews. This bird has been 
nown to eat green crabs, and it is therefore a more likely host for 
ie worm than the Dunlin. The Herring Gull is very common at 
toly Island and is constantly to bo seen flying about over the scaup, 
nother trematode was found in the liver of a specimen of Burcimm 
iKliitum from the scaup. The liver was full of long yellowish sporo- 
FSte containing tailed cercaria- (see Plate III., fig. VI.) The cer- 
uia is colourless and has two eyes rather far apart, one on each 
de of the pharynx. It is extremely contractile and constantly 
ftering its shape. It bears a large oral sucker leading into a con- 
ncuous lipped pharynx by an oesophagus which is sometimes in- 
sible owing to the contractions of the animal. A large median 
icker almost the same size as the oral sucker occurs in the centre, 
