90 STERELMINTHA. 



The phenomena which have been observed connected with the 

 multiplication of the Planarise by division are analogous to those 

 which we have witnessed in other acrite animals ; for it has been 

 proved, that if an individual be cut to pieces, every portion continues 

 to live and feel, from whatever part of the body it may be taken ; 

 and, what is not a little remarkable, each piece, even if it be the 

 end of the tail, as soon as the first moment of pain and irrita- 

 tion has passed, begins to move in the same direction as that in 

 which the entire animal was advancing, as if the body was actuated 

 throughout by the same impulse, and, moreover, every division, 

 even if it is not more than the eighth or tenth part of the crea- 

 ture, will become complete and perfect in all its organs. 



The mouth, in a few species of Planarise, is placed at the an- 

 terior extremity of the body, but generally it is found to occupy the 

 middle part of the ventral surface. Its structure is quite peculiar, 

 and admirably adapted to the exigencies of the creature : it con- 

 sists of a wide, trumpet-shaped proboscis, (fig- 39, 3 and 4,) which 

 can be protruded at pleasure, and applied to the surface of such 

 larvae or red-blooded worms as may come within reach, so as to 

 suck from them the juices which they contain ; or, if the prey be 

 small, animalcules and minute Crustacea are seized by it and con- 

 veyed into the digestive canals. The internal organs appropriated 

 to nutrition resemble in all essential points those of the Distoma ; 

 they consist of a multitude of blind tubes, hollowed out in the 

 parenchyma of the body, which, when distended with coloured 

 substances, are sufficiently distinct. The principal trunk, (fig* 39, 

 1,) which communicates with the proboscidiform mouth, soon di- 

 vides into three primary branches ; one of which runs along the 

 median line of the body towards the anterior extremity, whilst the 

 other two are directed backwards towards the tail. From these 

 central canals secondary ones are given off, which permeate all parts 

 of the body. There is no anal aperture, so that of course the 

 residue of digestion is expelled through the mouth ; but the nature 

 of the process by which defecation is thus effected is curious : 

 the Planaria, slightly bending its body, is seen to pump up through 

 its proboscis a quantity of water, with which all the branches of the 

 alimentary ramifications are filled ; the creature then contracts, 

 and, forcibly ejecting the contained fluid, expels with it all effete 

 or useless matter. 



Besides the arborescent tubes in which digestion is accomplished, 

 a rudimentary vascular system is distinctly visible, by which the 



