54 Art. 2.— T. Kaburaki : 



give SO firm a basis as does a soli'd body. The mechanism of the 

 movement is exactly the same as that mentioned in the preceding 

 part. Both the Rliabdocoeles and tlie Pofyclads are capable of 

 performing true swimming movements, i.e. movements which are 

 free in the water without contact with my solid body. So far as I 

 can learn in the literature, however, no oiie has ever placed on 

 record that a freshwater Triclad swims freely througli the water, 

 although Bardeen (2) has spoken of tlie worms h-eely niaking 

 progress through the water. With regard to this I luive no ob- 

 servation at present. 



A comparison with_ the movement of land planarians is made. 

 In them the movement, according to Moseley (54), is a combined 

 reaction, brought about by ciliary movement on the ventral surface, 

 by secretion of mucus, by rhythmical contraction waves passing 

 longitudinally over the venti-al surface and by snake-like move- 

 ments of the whole body, the muscular factors being more important 

 relatively to the ciliary component than in the freshwater forms. 

 The snake-like movement I am unal)le to confirm from observation 

 on the forms. 



Crawling is to be attributed to a purely muscular movement, 

 and is always caused by a successive alternation of the active 

 muscular contraction and stretching. When starting spontaneously 

 one side of the body at the posterior end attaches with more or 

 less firmness to the substratum and then immediately the posterior 

 half contracts; an instant later the opposite side stretches out far 

 in front, being slightly lifted, and fastens to the substratum. Then 

 accoi-ding to a longitudinal contraction which begins just at the 

 back of the head and runs posteriorly, the hind end is thrust for- 

 wards. Sucli looping fashion is repeated with great rapidity. 



At this point 1 will proceed briefly to bring out the relation of 

 the movements of the Tri clad s to those of other Turbellarian groups. 

 Most of the Rhabdocoeles swim through the w^ater by means of 

 cilia covering the whole body, as previously mentioned by a number 

 of investigators. In fact, the movement is not at all or ver}' little 

 dependent upon muscular activit}^ On the contrary, many of tlie 

 Pol3dcads usually perform a gliding mcn-ement, largely efïected by 



