32 S. GOTO. 



As has already been mentioned, the striped fibres are also present 

 in the posterior part of the body (PI. XVII, fig. 5), and this portion 

 is, as in the sucker, sharply separated from the surrounding part by a 

 distinct membrane of connective tissue (figs. 5 and 12). 



The striped muscular fibres have hitherto been observed, so far as 

 I know, only in the sheath of the proboscis of Tetrarhynclius^^ among 

 the Plathelminthes. 



Tristomum — As is well known, the anterim- suckers are, in this 

 genus, situated in a pair near the anterior extremity of the body, on 

 both sides of the mouth or a little before it. They are more or less 

 circular, sometimes perfectly so and sometimes a little, elliptical. 

 Internally the substance of the suckers is directly continuous with the 

 mesenchyma of the body, and the suckers are therefore to be regarded 

 merely as local expansions of the body. This view is strengthened by 

 the fact that the muscular fibres of the suckers are the direct continua- 

 tions of those of the body. The dorso-ventral fibres are arranged 

 exactly as in the body, with the only difference that they are here more 

 strongly developed in accordance with their task as the chief agent 

 of suction (PI. XXII, fig. 5). The longitudinal and diagonal fibres, 

 on entering the suckers, become niore or less intermingled with each 

 other ; but the former mostly radiate straight towards the periphery, 

 while the latter curve round, and are mostly arriinged more or less 

 concentrically \Yith. the circumference of the suckers ; the terminations 

 of both the groups of fibres being attached to the investing membrane 

 on the dorsal as well as on the ventral side. The circular fibres of the 

 body also enter the suckers ; but they here lose their typical arrange- 

 ment, and become interminofled with the diaofonal fibres. 



1). Pinttier — Untersuchungeu ii. d. Ban des Bandwurmkbrpers. Wiener Arbeiten, Bd. 3, 

 2. Hft., 1880. p. 50. 



