NATURAL HISTORY OF BRITISH FRESH-WATER LEECHES. 75
water and kill in Perenyi's fluid at about 70° C. For whole
preparations use Mayer's hydrochloric acid carmine (70%
alcoholic). Decolorize in 1% hydrochloric acid in 70% alcohol
until specimens have a light rose colour. Then wash in neutral
alcohol, clear in cedar oil and mount in balsam."
LIST OF BRITISH SPECIES OF FRESH-WATER
LEECHES.6
Sub-order I. RHYNCHOBDELLAE
Family I. Ichthyobdellidae.
Piscicola geometra, Linn.
Family II. Glossosiphonidae.
*Protoclepsis tessellata, O.F.M.
*Hemiclepsis marginata, O.F.M.
*Glossosiphonia heteroclita, Linn.
*G. complanata, Linn.
*Helobdella stagnalis, Linn.
Sub-order II. ARHYNCHOBDELLAE.
Family I. Gnathobdellidae.
*Haemopis sanguisuga, Linn.
Hirudo medicinalis, Linn.
Family II. Herpobdellidae.
*Herpobdella octoculata, Linn.
*H. atomaria, Carena.
*Trocheta subviridis, Dutrochet.
*Indicates species recorded from Essex.
Piscicola geometra, Linn. "Fish-leech." Plate VI.,
Fig. 1.
Description.—Body slender, cylindrical and semi-transparent. From
20-30 mm. long. Has well marked anterior and posterior suckers, the
former with two pairs of eyes. Posterior sucker has 14 dark rays with
a black spot in each of the intermediate areas, and is about twice the
diameter of the hinder portion of the body. Colour greenish, yellowish
or brownish, with a pair of lateral, pulsating vesicles on each somite
of the posterior region. Body dotted with small dark spots. Complete
somite with 14 rings.
Habits, etc.—Very active. Attaches itself to weeds and
stones by the posterior sucker and waves its body about until
prey comes within reach. It can swim well. It attacks most
6 The classification and nomenclature adopted is that of Harding. See p. 65 for family
characteristics.