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The British Leeches 
The three pairs of eyes are somewhat variable in position. The 
eyes forming the anterior and smallest pair are closely approximated 
(in an inner paramedian position) and lie, generally in ring 5, occasionally 
in ring 4 or in ring 6 ; one or both of them may be devoid of pigment. 
The eyes composing the second and third pairs are wider apart (in an 
outer paramedian position) and situated respectively in rings 7 and 8. 
71 rings. The male and female genital ducts have a common orifice 
between rings 28 and 29. Testes, 6 pairs. The anus lies between 
rings 70 and 71. 
Eggs attached to the ventral surface of the parent. 
Length, at rest, 10—13 mm.; width, at rest, 3—4 - 5 mm. 
Distribution, Food, etc. A sluggish species, common in England, 
in stagnant and slowly running waters, chiefly among aquatic plants. 
Its range probably extends into Scotland but its occurrence there does 
not seem to have been recorded. In Ireland it is found in a few 
localities but is not common (Scharff, 1898). It is widely distributed 
in central Europe and occurs in Sweden, in Sardinia (Blanchard, 1894) 
and in North America (Castle, 1900). 
It breeds in England in June and July : large individuals may carry 
more than 60 eggs. It is parasitic chiefly upon gasteropods. 
Varieties. Apathy (1888 b, p. 790) states that the colouration 
of this leech shows “ numerous transitions to a variety ( striata ) which 
is distinguished by intensely black transverse stripes, more or less 
interrupted, on every third ring.” Castle (1900, p. 42, pi. viii, fig. 38) 
finds in the United States all gradations between the clear yellow form 
and a form with transverse striae and an irregular longitudinal band on 
the dorsal surface, due to the presence of orange, dark brown or black 
superficial pigment cells. Dark brown or blackish pigment is rarely 
present in British examples of G. heteroclita. Houghton (1865) does 
not refer to it and among a very large number of individuals examined, 
I have not found one in which it occurred. Johnston however states in 
his Catalogue of British species (1865) that “the back is sometimes 
speckled with blackish dots.” 
In rare cases not only the eyes composing the first pair but also 
the right and left components of the second and third pairs are so 
closely approximated as to give the appearance of three single eyes. 
On this trioculate and triangular disposition Carena (1820) founded 
bis supposed species Hirudo trioculata. 
