4 HIRUDO. 



body where the posterior sucker joins it ; and here is the orifice of the 

 intestinal canal, as demonstrated by a continuous sanguinary stream 

 sometimes discharged from it. 



This animal is always of a dull or dingy colour., varying from oil green 

 to brownish, or in young specimens reddish-brown, bluish, or greenish, 

 but on the whole generally tending to oil green. A lighter spotted 

 stripe sometimes runs down the back ; and some of the young have ap- 

 peared reddish, encircled by lighter belts. 



Certain authors have ascribed two short horns in front to the Skate 

 Leech ; but I have never seen any of the genus Hirudo with prominent 

 external appendages, nor can I find that any such are known to the 

 Scotish fishermen. The aspect of the animal however is so peculiar, and 

 the skin being rough while all others are smooth, that it cannot be 

 mistaken. Plate I. fig. 1. 



I have not learned that any variety, such also as some authors 

 speak of, dwells in our seas. 



The Hirudo muricata has received a name most appropriate, as 

 indicative of its appearance, which no prudent practical naturalist would 

 have proposed to change. 



This animal preys on the living skate, and it is said also on some 

 other flat fish. The fishermen, who are not particularly veracious, affirm, 

 that they are to be found in dozens on a single skate, excavating the 

 very flesh. They say likewise, that they are very numerous about the 

 beginning of June ; and certain it is that at no time are they rare. 



The Skate Leech cannot ever be induced to feed in confinement, 

 though offered various animal substances, among which was a young 

 skate, extracted from its capsule. If cavities be actually seen in the 

 surface of adults, it is highly probable that the flesh has been consumed 

 to reach the blood, which seems to be the chief subsistence of the Leech. 

 Some species of fresh-water leeches are greedy of flesh, as we shall see 

 afterwards ; for it is an error to believe, as has been frequently asserted, 

 that the animals of this genus live entirely by suction. The streams of 

 blood discharged in confinement by the Skate Leech prove the quality of 

 its sustenance. 



