Aug., 1847.] 249 



water, turn upon the back, and by making- the ventral surface con- 

 cave, float about in the manner of the Ltmniadce. It appears to be 

 carnivorous in habit, or at least it attaches itself to animal matter, 

 dead or living, in preference to vegetable matter. When irritated, 

 it throws out a considerable quantity of very tenacious mucus. 



In structure it appears to be intermediate between the entozoic 

 Distomata and the annulose Hirudinoe. I could not detect any trace 

 of annulation, but I think that this alone would hardly be sufficient 

 to place it lower than the latter animals, because, in a closely allied 

 animal, the Gordius aquaticus, although there is no annulation in the 

 perfect animal, yet in the embryo state I find it to exist. 



The whole animal is composed of a delicate granular structure : the 

 only approach to muscular fibre is in the longitudinal striation of the 

 integument rendered more distinct by the pigmentum nigrum, a ra- 

 diated appearance around the oral orifice, and a faint transverse and 

 longitudinal arrangement of the granules entering into the composi- 

 tion of the proboscides, seen more or less distinctly in the continued 

 movements of these organs when slightly compressed beneath the 

 microscope. 



The digestive cavity presents the same dendritic arrangements as 

 in Planarzce generally,* but instead of posessing a single sucker or 

 proboscis, the full grown animal has not less than twenty-three ; vary- 

 ing, however, in this respect from three upwards, according to the age 

 of the animal. One of these proboscides joins the digestive cavity 

 at the posterior part of the anterior division, as usual, the others join 

 the remaining two divisions at their internal side in their course back- 

 wards. They are considerably longer, but narrower than in P. ladea,f 

 and when not in use are closely packed together within the animal, 

 so that when the latter is placed beneath the microscope and slightly 

 compressed, they will be seen pressing upon one another in such a 

 manner, that if one changes its position, it will be instantly occupied 

 by another. Those which are formed last are smallest, but they soon 

 gain their full size. 



When the animal feeds, the whole of them are protruded from the 

 oral orifice, the longest extending out full one-third the length of the 

 body. As they are all convergent to the same orifice, when fully pro- 

 truded the animal becomes puckered up and increased in breadth at 

 the expense of the length. In this state the anterior extremity is erected 

 and the posterior brought nearly to a right angle with it, so that it 

 looks as if sitting upon its prey apparently unconcerned, with itspro- 



*Duges, An. Sc. Nat. f lb. 



