NATURAL HISTORY OF BRITISH FRESH-WATER LEECHES. 77
places of attachment being the breast plumage, nasal cavities
and oesophagus. De Guerne (20) has shown that migrating
ducks may aid in the distribution of the species.
Distribution.—Britain:—R. Stort, near Little Parndon ; E.
London Waterworks, Tottenham ; Botanic Gardens, Regent's
Park ; Staines (H. W.) ; Histon, near Cambridge (Harding, 21) ;
R. Thames, Bourne End; New Forest (Blair) ; Aldenham
Reservoir (Miss Robertson, 38) ; Shropshire Union Canal
(Houghton, 28) ; Costessey, Norfolk (Brightwell, 9) ; Holy
Island Lough (Johnston, 32) ; Coldingham Loch, Berwickshire,
Cos. of Edinburgh and Linlithgow and the Isle of Bute
(Dalyell, 12).
Ireland:—Lough Neagh (Thompson, 42) ; Clonbrock: Santry,
Co. Dublin; Glenomeragh, Co. Clare (Scharff, 39).
Foreign:—Germany (Johannson, 30), France, Denmark,
Sweden, Finland, Prussia, Austria and Hungary ; Chili (Blan-
chard, 33).
Note.—An allied species, P. meyeri, has been recorded from Western
Europe. It differs from P. tessellata in the fact that the genital
apertures are separated by two rings.
Hemiclepsis marginata, O. F. Muller (Clepsine marginata).
Plate VI., Fig. 3.
Description.—Body flattened, claviform, more or less transparent.
The anterior portion bears two pairs of eyes and is spade-like in form.
Colour olive green or yellowish. Seven longitudinal rows of yellow spots
run along the back, the ventral surface is without spots. The posterior
sucker has reddish brown rays with yellow spots between. Length from
20 to 30 mm., and breadth from 2.5 to 5 mm.
Habits.—A fairly active leech which creeps about quickly,
but is unable to swim. Is found amongst water plants and on
the under surfaces of stones. It is parasitic upon fish and
when once attached may remain upon its host for some days.
It is an agent in the transmission of certain trypanosomes
which infest fish (ante p. 67). A specimen taken in May 1911
had 12 eggs attached to the under surface of the body. Another
specimen taken at Bletchingley in April 1912, had 60 eggs.
On hatching they attached themselves to the mother, but left
her about three weeks later. They were then about 10 mm.
long, and attached themselves to foreign objects by the dorsal
sucker and waved their bodies about as if in search of prey.
Distribution.—Britain :—Lake, Regent's Park ; Wake Valley,