8 RESEARCHES IN HELMINTHOLOGY AND PARASITOLOGY. 



straight in front, by contraction becoming convex or concave ; pos- 

 terior extremity abruptly pointed ; ocelli two, anterior, composed 

 of an oblong, semi-transparent (nervous ?) mass with an intensely 

 black dot of pigmentum at the internal posterior part ; ventral 

 apertures two ; oral aperture a little less than one-third the length 

 of the body from the posterior extremity, and very dilatable ; gen- 

 erative aperture half-way between the oral aperture and posterior 

 extremity. Colour black or iron gray, and in some younger speci- 

 mens latericeous. This animal I have only found in abundance in 

 the neighborhood of Professor Haldeman's residence, near Colum- 

 bia, Pa. In a spring in front of his house, thousands of them may 

 be seen gliding along the bottom ; some of them occasionally creep 

 up the sides to the surface of the w^ater, turn upon their back, and 

 by making the ventral surface concave, float about in the manner 

 of the Limniadse. 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 Hirudiuae. 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 (hrdms aqicaiiats, 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 iutegimient rendered more distinct hy the pigmentum nigrum, 

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

 and longitudinal arrangement of the granules entering the composi- 

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

 movement of these organs when slightly compressed beneath the 

 microscope. 



The digestive cavity presents the same dendritic arrangement as 

 in Planarise generally,* but instead of possessing a single sucker or 

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

 varying, 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 backward. Thej' are considerably longer but narrower than 



*Duges An. Sc. Nat. 



