37 
a fine vas deferens runs up to the vesicula seminalis, which is 
enclosed completely in the somewhat club-shaped cirrus sac The 
latter extends a little way behind the ventral sucker, and contains 
at its posterior end the vesicula seminalis, which is thick and 
shghtly crumpled up at first, then forms a loop, and finally runs 
straight to a cirrus surrounded by large cells. A true pars 
prostatica is absent. The male duct opens into a very small 
genital sinus, the outer genital pore being to the left, between the 
pharynx and- fork of the intestine. The ovary is ventral, and lies 
on the right in front of the foremost testis. It is three-lobed and 
Irom its posterior end springs the oviduct, giving off a dorsal pear- 
shaped receptaculum seminis with a Laurer's canal on the left 
Ihe oviduct then receives the vitellarian duct and shell gland and 
passes to the uterus, which winds in a few loops between the ovary 
and ventral sucker, and then runs up on the left side to a va-ina 
which opens into the genital sinus to the left of the male operLr 
Ihe eggs are not numerous (20-60)/- and measure 0-06 mm to 
0-08 mm. in length; they are a brownish yellow colour The 
vitellana are conspicuous, reaching ventrally from the extreme 
end of the body to the back of the ventral sucker, and stretching 
across the body behind the hindmost testis. They consist of small 
compact follicles, very numerous, and united by transverse canals 
giving off a transverse duct each side, which join in the vitellarian 
receptacle near tho ovary. 
Levinsenf found the larval stage of P. atomon (= Distomum 
Bud (?) Olsson) encysted in the amphipod ThemUto UbelMa 
(Mandt), and also in the stomach of Coitus sco, P u lS ; with the half- 
digested remains of this crustacean he found free capsules containing 
this Trema ode. The younger stages have not been found. 
The life history of P. atomon therefore probably runs as follows 
First host, unknown; intermediate host, Themisto UMlula ; final 
Host, Coitus scorpius and other fish. 
Distomum hacillare (Molin). (Plate II., fig. 1.) 
were 1 " l^f^ ™ A " gUSt tW ° B ^ meaa of 8 Nematode 
Were found in the intestine. Unfortunatelv, they were onlv 
jammed superficially at the time and then put away a Id he 
P eserving medium has so spoilt them that they are L ^ 
Jgefbr^a dsd ss^ttoo. gfae following note's show, I thin" 
*»Jfe^ SuvluvT * rCCimCn ' 13 ■ much ^Sor number than usual; Odhner 
T l 'p. cit., page (>7. 
