164 
The British Leeches 
Parasitic largely upon gasteropods, but preys upon a variety of other 
hosts. The larvae (“ bloodworms ”) of several species of Chironomus, 
which contain haemoglobin, are a favourite source of food and impart a 
scarlet colour to its crop. The whole contents of the body of the larva 
are extracted, leaving the transparent integument entire. 
Moore (1901) states that it attacks small annelids, injured fish and 
frogs, and Blanchard (1894 b) records it from the bodies of newts. 
Its range extends throughout the greater part of Europe into 
western Asia. It is found in Canada (Nicholson, 1873 , — Clepsine 
submodesta ) and in the United States from the Atlantic to the Pacific 
coast (Verrill, 1872; Blanchard, 1900; Moore, 1901). In South America 
it has been recorded by Blanchard (1896) from Paraguay and from the 
western slopes of the Andes. 
Dorsal plate. The dorsal chitinous plate which forms a character¬ 
istic feature of this species, has been shown by Apathy (1888 d, p. 202) 
to be the survival of an embryonic attachment gland, giving off a tuft 
of tenacious chitinous threads, like a byssus, which hardens in the water 
and serves, before its suckers are developed, to fix the embryo to the 
venter of the parent. The somewhat rough and hollow surface of this 
structure is a favourite place of attachment for colonies of Epistylis. 
A second example of a dorsal plate has been described by Blanchard 
(1900, p. 9) in the South American species, Helobdella scutifera. 
A provisional attachment gland, which leaves scarcety perceptible 
traces in the adult, occurs, according to Apathy ( loc. cit.) in the embryo 
of Glossosiphonia heteroclita and inconspicuous rudiments of similar 
organs have been described in several other species (Apathy, loc. cit. ; 
Nusbaum, 1885, p. 181 ; Dutilleul, 1887 a, p. 128). 
For the general anatomy of H. stagnalis see Castle (1900), p. 21 et 
seq. 
Sub-order II. ARHYNCHOBDELLAE. 
Fresh-water and terrestrial Hirudinea with red blood, without an 
exsertile proboscis, generally with jaws. A nterior sucker with a ventral 
aspect, not distinct from the body. Seventeen pairs of nephridia. 
Family I. GNATHOBDELLIDAE. 
With five, or rarely with four, pairs of eyes and, except in the 
Semiscolecinae, with three denticulate jaws. Eggs enclosed in a free 
spongy cocoon which is deposited above the water line. 
