TAPE-WORMS OF THE SUB-IAMILY AYITELLIXIX.E. 359 



The course of tlie canals in the scolex is somewhat compli- 

 cated, but can be reduced to quite a simple sciieme. If it is 

 remembered that the riglit and left halves only commuuicate 

 by a single loop situated at the apex of the scolex, and that 

 the dorsal and ventral canals of each side, after mountino- 

 through the scolex, meet and join each other just at tlie 

 apical connecting loop, it will be seen that the whole can be 

 reduced to the scheme oiven by v. Janicki for Inermicepsifer 

 in a paper to be published shortly. The actual plan of the 

 canals in the scolex is, howev^er, complicated by the fact that 

 the ventral canal forms a large number of loops and turus 

 before reaching the apex. The course of the dorsal canals, 

 on the other hand, is quite straight. 



Before commencing the description of the course of the 

 ventral canal it is necessary to explain the terminology to be 

 used. I must distinguish between dorsal and ventral suckers, 

 also between right and left suckers; the median face and the 

 lateral face, the outer angle formed by two suckers and the 

 inner angle formed by two suckers, and the base and apex of 

 a sucker. 



Dorsal and ventral require no further explanation ; the 

 median face of a sucker is that side which faces a line divid- 

 ing the right dorsal and ventral suckers from the left dorsal 

 and ventral suckers ; similarly the lateral face is that side 

 which looks towards the line separating the two dorsal from 

 the two ventral suckers. The outer angle formed by two 

 suckers is the angular space between the suckers near the 

 subcuticula, the inner angle the coi-responding space or angle 

 opening on the medullary zone of the scolex. The base is the 

 convex end, turned towards the strobila, and the apex the end 

 of the sucker containing the mouth of the sucker (see diagram). 



It has already been stated that the ventral canal in tlie 

 proglottids lies lateral to the dorsal canal. Following the 

 canals from the strobila into the scolex, we find that their 

 relative positions change close to the scolex, the ventral 

 canals lyiug internal to tiie dorsal canals. 



The left ventral canal (fig. 5), on entering the scolex, turns 



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