HIRUDO. 31 



sucker is brought forward to complete the step. But the mode of pro- 

 gression will be better understood from inspection than by description. 

 Six black eyes or ocular specks are disposed in three pairs on the surface 

 of the anterior extremity, fig. 3. The posterior extremity has u very 

 firm adhesion by the sucker. A margin of peculiar conformation, waved 

 and tuberculated, environs the body. Three tubercles, susceptible of 

 elevation and depression, rise from each convexity, fig. 5. The various 

 hues of the animal are considerably modified according to habitation, 

 age, and sustenance. Young specimens are dingy yellow. Grey is 

 always predominant in adults ; the back generally ash grey, with two 

 rows of short dark streaks. Some are spotted white, many altogether 

 greenish, or very dark. Such diversity appears in the disposal and the 

 fashion of the colours, that it is probable they will afford sufficient means 

 for establishing more than one variety. 



Where transparency admits, the interanea of all leeches, filled with 

 the blood of other animals, present a curious and interesting object. 

 Here there are ten lateral cells diverging from each side of a main trunk 

 in the middle, all connected with a common proboscis, and coloured ac- 

 cording to the nature of the food absorbed by it. It was from the dis- 

 covery of this tongue or proboscis, other leeches having only substances 

 like indurated glands for teeth, that induced Dr James R. Johnson to 

 constitute for this species the genus Glossipora. 



The natural abode of this species is in lakes or ponds, on the under 

 surface of stones, on decaying wood, or in the recesses formed by the 

 folds of the Iris and other aquatic plants. It frequently assumes a 

 supine position, remains a long time motionless, or affixed by the sucker, 

 undulates its extended body like some others of its kind. It is often 

 difficult to be removed without injury, but it always drops off spontane- 

 ously on very short exposure to the air. 



The H. complanata feeds abundantly on both animal and vegetable 

 substances. It is greedy of mussel, dwelling long over it, and absorbing a 

 great quantity. From this quality of food the body is often stained of 

 greenish hue, though the interanea be less conspicuously distinguished 

 by repletion. But this indicates the dispersion of the sustenance through- 



