46 HIRUDO. 
those with eight, the eye is disposed in two different arrangements, being 
either marginal, or in four pairs. 
The length of the specimens of this species when quiescent, was from 
six to more lines; when extended about fourteen lines. General form 
not unlike the Medicinal Leech. Form of the head lanceolate or trout- 
shaped. Eyes two, black, in front. The viscera consist of thirteen pair 
of transverse sacs, sufficiently conspicuous in some specimens. The body 
is composed of numerous segments slightly indented. 
The predominant colour is yellow, sometimes very vivid, sometimes 
dusky ; and there are specimens whose contrasting hues expose four 
longitudinal rows of beautiful yellow spots, running down the whole 
back to the sucker, which itself has a marginal circular row. Under the 
microscope these, so ornamental to the eye, prove to be only irregular 
transverse short marks. 
Though the general form of the animal while quiescent corresponds 
with that of the medicinalis, it is not so thick, plump, and heavy as the 
tessellata, nor alike tremulous. Also some of the young at an early stage 
appear quite cylindrical. 
Much of the beauty of this animal depends on the colour. Besides 
the four rows of yellow spots down the whole back, there is a marginal 
row on each side, which can be seen from below.—Plate V. fig. 1. Hirudo 
flava, young ; 2, the same, enlarged ; 3, head more enlarged ; 4, another 
specimen, natural size, back ; 5, the same, enlarged, sucker a; 6, belly 
of the specimen fig. 4; 7, the same, enlarged, sucker @ ; 8, head more en- 
larged, shewing the eyes. 
It has not appeared what is positively the food of the yellow leech. 
The ponds wherein I have found it abound more with decaying leaves 
than with anything else which was likely to afford it sustenance, and it 
always reposes on or under them. 
This species breeds chiefly from May until August, and is a fine 
example of what, in more important living beings, might be called a 
marsupial gestation. Hence a great correspondence is shewn with the 
nature of those with which it has been more associated, as with the dzn- 
oculata and complanata, 
