DUTROCHET'S LAND LEECH IN ESSEX. 219
turned over as the leaves of a book, but in handling the species-
papers on which the specimens are mounted, they should be
lifted up (using both hands), and carefully placed one on the
top of the other and then replaced in their proper order. The
immediate work that remains to be done is the publication of
a list, using the nomenclature of the British Museum List, of
the species that are not yet in the Herbarium. The work
already done will possibly give the necessary impetus to the
collecting of specimens to fill up the omissions ; partly by original
field work, partly by the medium of exchange clubs and possibly
by purchase. A work in which all can help.
The Herbarium is contained in Cabinets constructed on the
British Museum principle, which at present number twelve ;
these will, of course, be added to as necessity arises.
DUTROCHET'S LAND LEECH (TROCHETA
SUBVIRIDIS) IN ESSEX.
By HENRY WHITEHEAD, B.Sc.
MR. J. Bostock and I found two specimens of this interesting
leech in a small stream near Theydon Bois in April of
this year. One of the specimens was found on a mass of vegetable
matter which had fallen into the stream, and the other was taken
swimming. One of our captures was accidentally killed during
the process of identification, but the other has been safely
installed in a vivarium in which some soil and a tuft of grass
has been placed alongside a saucer containing water. The
leech spends most of its time in the water and seldom indulges
in terrestrial exercise, though this may happen during the
night. Dutrochet's Leech is perfectly harmless and is unable to
suck the blood of mammals and, like the Horse Leech (Haemopsis
sanguisuga), feeds on earthworms, which are swallowed entire.
The surviving specimen is about 100 mm. long and 7 mm.
in diameter at the widest part when at rest. There is a well
developed sucking disc at the posterior end, and at first glance
the species might be mistaken for Haemopsis sanguisuga. The
colour is a dark brownish green, and two dark brown bands
extend along the dorsal surface, while the ventral surface is of a
lighter tint. One of our specimens shows a distinct clitellum
about the anterior third of the body. Typically there are four