W. H. LEiGii-SiiAiirE 
215 
12-vesicled animal have the non-respiratory vesicles, and the 11-vesicled 
animal be destitute of them. 
Confusion also arises in the descriptions, because writers on leeches 
will not be careful enough to differentiate between segments and annuli, 
often using the word “ rings ” to cover both, leaving it to the imagination 
of the reader to discriminate which is meant. 
Summary of the characters leading to the belief that Calliobdella lophii 
is a ■perfectly stationary parasite never quitting its host. 
1. Extreme size of the posterior sucker. 
2. Weak development of the longitudinal muscle layer. 
3. Its occurrence on only one host. 
4. Several members (5 and 4) being found together on one host, 
hence rendering fertilisation possible. 
5. The extreme care with which the living leech, when moving, 
places the posterior sucker as exactly as possible in the position pre¬ 
viously occupied by the anterior (as observed by Hesse and myself). 
6. Reduction from two caeca to one. 
7. Shrunken aspect of caecum, with lumen partly obliterated. 
8. Empty condition of caecum, and alimentary tract in general. 
9. Its rarity. 
Conversely the stationary habit of the leech satisfactorily accounts 
for its rarity. 
These suggestions are of importance, inasmuch as though we have 
a new parasite on our coasts, it is not likely to spread. 
Generic characters. A leech divided in a marked manner into a neck 
and a body. Each body segment consists of 6 anniili. Along the side 
of the body are eleven pairs of pulsating respiratory vesicles. The 
common terminal portion of the ductus ejaculatorii opens into a large 
and wide bursa which can be protruded, wheremth is formed a copulatory 
apparatus which is at least as long as the breadth of the body in the same 
place, and has at its end a peculiar muscular part. A pair of vesiculae 
seminales are present. There are no eyes. Blackish-brown star¬ 
shaped pigment cells are absent. 
Specific characters. Van Beneden and Hesse separated 3 species : 
C. lophii, C. jyunctata, and C. striata. Other authors recognise 4 or only 
2, giving them various names, but all retain the species G. lophii. 
Apparently its only host is Lophius piscatorius. It is characterised 
by the extreme size of the posterior sucker, it being more than twice 
