20 
Lernaeopoda scyllicola n. sp. 
I may here record that the dogfish consigned to me from Plymouth 
during the year 1917, bore remarkably few examples of Lernaeopoda scyllicola $. 
In no case were more than two present, and about half the total number was 
devoid of them. As far as the present year has gone (April, 1918), the number 
of parasites present appears to show a slight increase. Dividing the number 
of male dogfish examined into the total number of parasites taken yields the 
following “periodicity table” of females: 
1914 (the latter six months) 
1 Q1 5 
JL t/ JL ••• ••• ••• 
1916 ... ... ... ... 
1917 
X t/ X I ... ... ... ... 
1918 (the first three months) 
4 
4 (maximum 6) 
3 
1 
2 
Only two individuals of L. scyllicola $ were observed on female dogfish during the whole 
of the foregoing period, and those during 191x5. Besides the usual locations within the 
extra-cloacal aperture, and on the grooves of the claspers, I have recently found L. scyllicola $ 
in other, probably fortuitous, situations. In April 1918 I took a specimen outside the 
extra-cloacal aperture posterior to and between the fusion of the pelvic fins and the body, 
and one specimen (sexually immature) from the extreme tip of the right clasper. Although 
specimens from the clasper grooves are not uncommon, it is an extraordinary coincidence 
that hitherto I have only taken them from the dogfish’s right clasper, and never from the 
left. I have heard it authoritatively stated by mariners and sea-faring men that sharks 
and other Elasmobranch fishes at the natatory “roll,” or when they turn over to seize 
their prey, invariably depress the right side of the body, and I have observed the same 
phenomenon in the rolling of porpoises. Possibly in the rolling dogfish the left clasper is 
elevated, and the Copepod larvae sucked against the right clasper. I believe that the 
cloaca of the female dogfish would not be opened at the natatory roll, the pelvic fins having 
a different conformation posteriorly from those of the male, which may account for the 
rarity of L. scyllicola upon female dogfish. 
From recent observations I conclude that the length of the “arms” (2nd maxillae) is 
so liable to variation, in the genus Lernaeopoda at any rate, that no reliance can be placed 
upon it as a specific character. The “arms” of female specimens taken on the clasper 
grooves are invariably much shorter than of those attached within the extra-cloacal space, 
while the one attached to the tip of the clasper had “arms” barely longer than the 
cephalothorax. Conversely the more anteriorly are the parasites located, the longer do their 
“arms” become, those situated practically within the cloaca and around the urino-genital 
papilla possessing the longest “arms” of all. It is obvious that these admit of, and possibly 
require, more movement about a fixed centre (the bulla), while such radial movement 
would be disadvantageous to an individual affixed to a clasper, as it would be liable to 
accidents causing detachment. The other, shorter-armed genera of the Lernaeopodidae 
are found upon the gills of various fish, where there is little freedom for movement, so that, 
in fine, the length of the “arms” has a biological rather than a specific significance. 
DESCRIPTION OF THE MALE. 
Body. The outline of the animal is best seen from Figs. 2, 3 and 4. The 
animals are of a yellowish white colour, though, as a rule, paler than the 
female. Length 2 mm. or about one third the length of the female which, 
though sexually mature, has not yet attained her full growth. The body is 
