6 HIRUDO. 



Plate II. fig. 8 ; which 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 Caliyus 

 curt its 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 occur along with the 

 Udonetta. 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 agglutinated 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 



