438 
Marine Cercariae 
contained cercai’iae are colourless measuring 0‘18 mm. in length 
including the tail, tail O'Olo mm. nearly square. Oral sucker 0’035 mm. 
armed with a stylet anteriorly cleft. By the side of the stylet open the 
four ducts of the stylet glands. The glands are conspicuous in front 
of the ventral sucker which measures 0’04 mm. across. The excretory 
vesicle is lined by very large conspicuous cells and opens posteriorly. 
The alimentary canal is not developed. 
Further life-history not known. 
Gercaria brachyura Lespes (1857, p. 113). 
(PI. XXVII, figs. 14-16.) 
Occurs in the digestive gland of Gihhida cinerea from Loch Ryan 
and Millport. In two per cent, from Millport and only found once at 
Loch Ryan. 
The sporocysts like the last species are a brilliant orange colour but 
they are very active and constantly change their shape. The young 
forms are redia-like although without pharynx and intestine, often 
showing processes like the ambulatory processes of a redia. This fact 
was noticed by Pelseneer (1906, p. 168) in what he takes to be this 
speciesk The older redia measures 1’2 mm. in length. The cercaria 
without its tail measures 0'24 mm. in length. The oral and ventral 
suckers are nearly the same size, the oral slightly larger than the 
ventral, oral sucker O'Oo mm. across when circular but often appears 
longer than it is broad. I could not see the stylet mentioned by 
Lespes and Pelseneer does not mention it. The stylet glands however 
are very conspicuous in front of the ventral sucker, opening by four 
ducts near the oral sucker. A pharynx is sometimes to be seen pre¬ 
ceded by a short prepharynx, but I could not see any more of the 
alimentary canal. The excretory vesicle is lined by very thick cells. 
The body in some of the specimens was covered with minute spines. 
The tail usually looks broader than long and is slightly cleft posteriorly. 
I think it is very likely to be a different species from Pelseneer’s 
as his ventral sucker is larger than the oral and there are other small 
differences. It may be distinct from Lespes’ species also, but they are 
all very much alike. 
The further life-history is unknown. Pelseneer observed some of 
his specimens encysted in Gihhida cinerea. The tails had disappeared 
in three out of four specimens. In the fourth it had just come off. 
' Pelseneer refers to it as Cercaria pachycerca Lespes. 
