Japanese Freshwater Triclads. 5]^ 



Pearl (57). Under normal conditions contact of one individual 

 with another does not start the feeding reaction, which is a purely 

 reflex phenomenon, capable of being started only by a certain set 

 of stimuli. 



As regards the obtaining of food, I have made an observation 

 in one case of PI. gonocepJiala. The worm, on meeting a certain 

 Crustacea in its path in the course of movement in a dish, stops an 

 instant, slightly raises the head and lets it drop down till it 

 touches the said minute animal. ( )wing to currents produced by 

 undulation of the auricular lobes as well as by means of cilia which 

 cover the head-surface, the anterior end closes down over tlie whole 

 body, and then apparently squeezes it by contraction of the mus- 

 cles on the ventral surface of the head. While the reaction is 

 taking place the worm as a whole stops its progressive nio\ements 

 and remains quiet. After squee-zing the food animal the worm 

 starts gliding ahead on to the food. In the process the mucus, 

 which is secreted at all times over the surface of the body, is con- 

 sidered, as it seems to me, partly to serve as an important factor in 

 securing food. The worm passes forwards up to the point where 

 the opening for the extrusion of the pharynx is located. Then the 

 pharynx is extruded and feeding begins. 



Resjih'atloR. — It is self-evident that the planarians, although 

 provided with no special organs, are capable of breathing i.e. of 

 taking in oxygen contained in solution in the water and dis- 

 engaging carbonic acid. The process of respiration is carried on 

 through the epidermis or through the internal organs which stand 

 in direct communication with the surrounding water. Tliey are 

 all very sensitive to the amount of the air (oxygen) contained in 

 solution in the water. In aquarium, when there begins to be only 

 a slight overloading with carbon dioxide, many individuals can be 

 seen making their way to the top, where there exists a layer of 

 fresh water, avoiding the foul depths. Occasionally they prefer to 

 remain near the top for a long time, staying quietly near the edge 

 or creeping about very slightly along the surface film of water. So 

 far as our observations go, the worms find, in general, their most 

 suitable habitation entangled in a mass of algae or creeping over 



