TAPE-WOliMs OF THE SUr.-rA:\ni.Y AVITKLLTXIX-i:. 



327 



cells in turn are in contact with the parenchvina, as described 

 lower down for the . excretory canals in the scoles of 

 Avitellina centripunctata (Riv^olta). 



The doi'sal canals do not appear to be connected by trans- 

 verse commissures, nor to be connected to the ventral canals 

 or their transverse commissures. 



The lumen of the ventral canals measures np to 58 fx by 

 50 /< ; the dorsal canals ai-e about 30/.( by 25 /t in diameter. 



According to the state of contraction, the course of the canals 

 can vary from being nearly rectilinear to very closely spiral. 



Text-fig. 1. 



d dc 



Diagram of Stilesiu liepaticn. (For explanation of letters see list 

 of iilibreviations at end of paper.) 



Calcareous corpuscles are found in the medullary substance 

 of the scolex and at the posterior ends of the segments; their 

 diam.eter is 10 u. 



The muscles of the strobila ai'e not very strongly developed. 

 The longitudinal muscles are in two laj-ers, the inner consist- 

 ing of bundles of about twelve, the outer of three or four 

 muscles. The transverse muscle is weak, as is also the dorso- 

 ventral muscle. 



The sexual organs differ greatly from Wolffhiigel's descrip- 

 tion. In the first place each segment (of the type also !) has 



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