A Neio Leech 
•7 
purpose (described below, see also Figs. 1 and 2), causing a constriction 
on the body of the host proximal to the anus. The leech appears to 
be a stationary parasite not quitting the papilla that it has induced; 
it is conceivable that it may be a faecal feeder. 
Since in my paper on Calliobdella lophii {loc. cit.) I gave, as one of the reasons 
for believing the latter leech to be a stationary parasite, the fact that four or five 
specimens were found together on one host, hence rendering fertilization possible, 
I was at first at a loss to perceive how fertilization could be effected in Ganymedes 
cratere. This gives the clue to the second reason for believing the host to be 
Callionymus lyra for in this fish, practically alone, although there is no actual 
copulation, there is a courtship, and a pairing or mating which has been admirably 
described at length by Holt^. Pendmg the mating of the fishes, I beUeve the 
leeches are able to copulate; during this process I consider one of the leeches is 
practically bound to be detached from its host, and probably perishes. If, however, 
the other leech lays many eggs that are fertile the balance in nature is maintained. 
Owing to the anal papilla being so prominent, by contrast the uro-genital papilla 
seems not so prominent, or perhaps its size actually has been diminished by the 
superabundant growth of the former. 
(It would be interesting to discover if there is any paking or courtship in Lophius 
piscatorius which could be utihsed by Calliobdella lophii.) 
Body. The leech is divided into two distinct regions, a neck region 
which is short and bare, and a body or abdomen, the latter carrying 
laterally rounded vesicles described below. The animal is circular in 
section in the neck and in the short anal region, but in the abdominal 
region it is greatly flattened dorso-ventrally, so that the animal, taken 
as a whole, presents the outline of a minute vase. The length when 
living was 0-8 cm., and this seemed to me a normal measurement, for 
the leech appeared incapable of any appreciable extension when alive, 
and did not exhibit contraction to any extent when dead. The colour 
is brown ochre, the suckers being paler, and the abdomen darker; the 
whole gradation of tints resembhng those met with in the brown alga 
Fucus. There are no special coloration characteristics, nor papillae, 
except one papilla hereinafter mentioned. 
Suckers. As is usual vdth leeches there are two suckers, one at 
either extremity of the body. The anterior sucker is crateriform, 
surrounds the mouth, and is characterized by its great size, being nearly 
as broad as the maximum width of the abdomen and over four times 
the size of the posterior sucker, this being the reverse of what obtains 
in Calliobdella lophii. The anterior sucker is surrounded by a thick 
Holt (19. IV. 1898), Proc. Zool. Soc. p. 281. 
