gß ' Art. 2. — T. Kaburaki : 



When tlie worm passes from the resting or contracted condi- 

 tion into movement, one can see the lengthening of the body, 

 which is meant by extension of the body. Piobably the most 

 important sets of muscular fibres for producing the general exten- 

 sion are the circular and dorso-yentral. The contraction of the 

 former must cause the body to lengthen, and the contraction of the 

 latter must bring about the tiattening seen in the fully extended, 

 gliding animal. Of course, the transverse muscles assist, b,y their 

 contraction, in the extension of the body. It is self-evident that 

 contractions of any of the sets of fibres may take place in localized 

 region, producing extensions or contractions of that region, accord- 

 ing to the set effected. Tlie feeling movements of the liead are 

 efïected in this way. The extension and extrusion of the pharynx 

 are brought about by contraction of its well-developed circular 

 muscles. 



Tile animal in the coui-se of gliding raises the anterior part of 

 the body off the bottom so as to form an angle with the rest of the 

 body. The head is in constant though slight feeling movement, 

 without being held in a fixed raised position. Usually the head is 

 moved up and down, and swept from side to side, while at the 

 same time the tentacular or auricular lobes, though slightly un- 

 dulated, are fully extended and raised. The head region acts in 

 movement as an organ which is constantly testing the environment 

 as the worm proceeds. 



Reproduction by Fission. — The light which observations have, 

 up to the present, thrown on the phenomena of fission in the 

 Triclads is considerable; the revision of the literature has been 

 made by Stkinmann (~2), who divides the normal fission of them 

 into three groups. So far as my observations go, Fl. vivida and 

 Folt/. ijimai \'erv frequently reproduce b}^ fission. In the former 

 the division takes place quite similarly to that known in Fl. alpina 

 Dana. First a furrow appears at the place where division is to 

 occui" it deepens, finally leading to separation of the parts. There 

 were not infrequently found cases in which the dividing bodj^-parts 

 were still connected by a narrow l;)and of tissue, which no doubt 

 would soon break off by the motion of crawling. 



