6 HIRUDO. 
Plate I. fig. 8 ; whith work professes to contain certain figures deline- 
ated after Nature. I have never seen either fresh-water or marine 
leeches with appendages of any kind ; and although one foreign animal 
has been incorporated with them, I apprehend that it should be removed 
to another genus. But, in treating of the Hirudo muricata, it is not im- 
probable that some superficial observer has mistaken the vesicles for 
horns. 
Among the various conjectures which I indulged on the subject, 
that seeming the most probable, centred in the vesicles being animals of 
parasitic, or some organic structure susceptible of protrusion, and retrac- 
tile ; and thus I left them for many years. 
But, after the facts above narrated in the history of the Cualigus 
curtus occurred (Vol. I. p. 248), and having reverted to the subject, it 
appeared to me that the mysterious animal was to be identified as a 
variety of the same race. In this I was confirmed by observing figs. 2 and 
3, among the various delineations which sometimes oceur along with the 
Udonella. Such was the solution of the enigma.—Plate I., figs. 1-10. 
The Skate Leech propagates by eggs or capsules, of very remark- 
able configuration, more or less numerous, according to the fertility of 
individuals ; and they appear either singly, which is rare, or in a con- 
siderable group,—perhaps fifty on the exterior or interior surface of a 
shell—Fig. 11. 
The capsule consists of a sole, a short stalk surmounted by a spheroid, 
with a distinct umbo on the side. The capsule altogether is about three 
lines, and the spheroid which contains the embryo, or leech, about two 
in diameter. 
Such capsules are firmly agglutmated by the sole to the substance 
whereon they are deposited. They are originally white, or of the faint- 
est carnation, of a fine soft downy aspect, with the neck orange or yel- 
lowish. They darken gradually from the time of production, and in four 
or five days, the original white is converted to olive-green, or dull wax- 
yellow. They are produced singly, free of all gelatinous matter. 
The capsule is a very singular object, quite peculiar ; insomuch that 
it bears no resemblance to the ovum of any other animal. How many 
