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. RHYNCHOBDELLiE 
Family I. Ichthyobdellidje. 
Piscicola geometra, Linn. 
Family II. Glossosiphonidje. 
*Protoclepsis tessellata, O.F.M. 
*Hemiclepsis marginata, O.F.M. 
*Glossosiphonia heteroclita, Linn. 
*G. complanata, Linn. 
*Helobdella stagnalis, Linn. 
Sub-order II. ARHYNCHOBDELLiE. 
Family I. Gnathobdellid^e. 
*Hcemopis sanguisuga, Linn. 
Hirudo medicinalis, Linn. 
Family II. Herpobdeli.id,e. 
*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. 
