W. Nicoll 
239 
in those fishes is therefore nine out of 31, i.e. about 29 “/o- If did 
not occur in any other species of fish so that it is in all probability a 
specific parasite of the Lophobranchii. In Nerophis aequoreus it was 
accompanied by Podocotyle atomon. 
It bears a very close resemblance to the other species of Podocotyle 
but differs from them chiefly in the noticeable shortness of the cirrus 
pouch. 
The specimens varied in length from 2’2 mm. to 5‘9 mm. The 
smallest specimen was obtained from Nerophis aeqiioreus and had just 
begun to produce ova, so that evidently this species does not attain 
maturity so early as P. atomon. Some mature specimens of the latter 
measuring little over 1 mm. were obtained from the same fish. 
Measurements were made of five of the largest specimens, the average 
length of which was 5'36 mm. (4'55-5’95 mm.). The greatest breadth 
(0'78mm.) occurred usually at the testicular region, but the breadth 
across the ventral sucker was almost as great and in one case greater. 
The greatest breadth is therefore about 1/7 of the length. In a fully 
extended specimen it may be as small as 1/9. The species is therefore 
more elongated than P. atomon but less so than P. reflexa. The body 
is not much flattened and the ventral sucker is usually prominent. 
The oral sucker has a diameter of ‘38 mm. and the ventral sucker 
measures 0'43 x 0'55 mm. The latter is situated at a distance of r2.5 mm. 
from the anterior end, the neck therefore being somewhat more than 
1/4 of the body length. 
There is a very short prepharynx and the pharynx measures 0T9 mm. 
in diameter. The oesophagus is about as long as the pharynx (0T7 mm.), 
and the intestinal diverticula extend nearly to the posterior end of the 
body becoming slightly dilated during their course. 
The excretory vesicle reaches the anterior border of the ovary. 
The testes are separated from each other by a short distance (0'21 mm.). 
They are oval with their long axes slightly tilted from the middle line, 
the anterior end in both cases being usually directed towards the left 
side. They overlap the intestinal diverticula only to a very slight 
extent. Their dimensions are 0'57 x 0‘47 mm. Between the posterior 
testis and the end of the body there is a space a little over 1 mm. (1/.5 
of the body length, but this varies from 1/6 to 1/4). The genital aperture 
is situated a little in front of the intestinal bifurcation, decidedly 
towards the left side. The cirrus pouch is short and rather stout, 
extending at most not further than the middle of the ventral sucker. 
The vesicula seminalis is accordingly much more compact than it is in 
