Our Fresh-Water Planarice. 449 



of suction is due, and the passage of nutritious particles into 

 the ramifications of the stomach and digestive apparatus. It 

 is most curious to watch the movements of a planarian 

 proboscis when forcibly detached from the body of the worm ; 

 it almost seems to enjoy a separate existence for a time ; it 

 may be seen to open the orifice and swallow the pulpous 

 particles of its own body, then by contracting, to eject them 

 through the other end. This tube is in contact with the 

 stomach and digestive system, and opens out into it; its 

 basilar portion being apparently connected with the stomachal 

 walls by a very thin transparent membrane, very easily 

 ruptured. The digesive apparatus in the true Planarice 

 consists of a number of arborescent ramifications ; there are 

 three principal trunks, which unite about the centre of the 

 body and receive the particles of food supplied them by the 

 proboscis; one" of these trunks proceeds in a direct line 

 upwards towards the head, along the mesial line of the 

 body, and from it on either side there are numerous branched 

 coecal appendages ; the other branches immediately diverge 

 and pass down the sides of the body, again converging towards 

 the posterior extremity. This arrangement is very apparent in 

 Planaria lactea, in which the coecal appendages are most 

 numerous; in the other species, owing to the opacity of the 

 body, it is not so readily seen; slight pressure with the 

 compressorium, however, reveals a similar structure. The food 

 of the Planarice consists of infusorial animalcules, small naid 

 worms, the blood of which they suck, sometimes, according to 

 Duges, without perceptibly piercing their skins. The same 

 observer states that animalcules of the family Cyclidina are 

 sometimes found alive in their digestive organs. That they 

 have, however, cannibal propensities and devour each other, I 

 have myself frequently witnessed; this character, according to 

 my own observations, belongs more especially to the species 

 Polycelis nigra, and P. brunnea ; it is curious to see the 

 rapidity with which one of these fellows bores a hole into the 

 body of one of the large Planaria lactea, and crumbles him into 

 his component particles. The attacking enemy throws his body in 

 a fold over some portion of its victim, and immediately begins 

 to bore into him with his proboscis; this boring very soon 

 reduces a part of the body of the victim into minute particles 

 which are sucked up by the proboscis, as it makes its way 

 along. The Planarice, like the parasite Trematoda, are destitute 

 of an anus, the undigested portion of their food being regur- 

 gitated through the suctorius tube. 



The circulation in these animals is described as consisting of 

 a mesial and dorsal canal and two lateral vessels, from which 

 proceed in all directions, a fine cutaneous network of minute 

 VOL. XII. — no. vi. G G 



