M. V. Lkbour 
0'28 iTira.-0'32 mm., the greatest breadth usually being at the beginning 
of the posterior third of the body. The oral sucker is smaller than the 
ventral,measuring 0 04imm.-0‘06mm.acros.s,the ventral sucker measuring 
O'Ob mm.-0'08 mm. Both are circular in outline. The oral sucker is 
situated at the extreme anterior end of the body and leads by a circular 
aperture to the prepharyux which may be bardly recognisable when 
contracted but may measure as much as 0'04 mm. in length. The 
pharynx is large and muscular and measures 0’03 mm. in length 
and is rather longer than broad. The oesophagus is slightly longer than 
the pharynx and forks at a distance of 0'06 mm. in front of the ventral 
sucker. The intestinal caeca reach to the level of the posterior end of 
the ventral sucker. The ventral sucker is situated some way in front 
of the centre of the body and has a circular apertui’e. 
The excretory system consists of a posterior vesicle which is Y shaped 
and gives off lateral ducts, the flame cells at the ends of the smaller 
branches being very conspicuous. Tbe reproductive organs are far 
advanced in development. The testes lie just behind the ventral sucker 
and are large, lobed organs of a roundish form. Each measures about 
O’] 3 mm. in diameter. Ducts arise from these but could not be followed ; 
they spring from the anterior margins slightly to the inner side. The 
cirrus pouch lies in front of the ventral sucker and is well developed 
although the genital pore is not open and apparently the right end is not 
yet joined by the vasa deferentia. It is full of large nucleated cells and 
the vesicula seminalis is not formed. The ovary is conspicuous and lies 
on the right of the ventral sucker, none of it extending behind. It is 
roughly three-lobed and gives off a winding duct which loops behind 
the ventral sucker and then runs upwards, curving as it goes and 
enlarging to reach the left side of the cirrus pouch. The shell-gland 
complex could not be made out and probably is not completely 
developed. The vitellaria are of the typical Maritrema form and make 
a nearly complete wreath round the region behind the ventral sucker, 
running round the lateral margins and the posterior margin and then 
bending inwards in front of the testes and nearly joining, but leaving 
a small gap anteriorly. No vitellarian receptacle is as yet formed. The 
vitellaria consist of small rosettes of yolk material. 
Hitherto no larval Maritrema has been known for certain, although 
Cercaria oocysta sp. inq. and Cercaria piriim sp. inq., both from 
Pal'udestrina stagnalis, seem to belong to this genus or to one closely 
allied (Lebour 1912 and Nicoll 1907 b). My suggestion that the habit 
of encysting in sporoc 3 'sts (as these cercariae do) may distinguish this 
