360 LEWIS HENKV (iO[J(!(r. 



at right angles to its course, running horizontally towards 

 the base of the dorsal sucker, then rising vertically it 

 proceeds up the lateral surface of the sucker to the level of 

 the bottom of the hollow of the sucker ; it then turns over 

 and proceeds downwards parallel to its ascent. Arriving near 

 the base of the sucker it gives off a short branch, Avhich runs 

 towards the median outer surface of the sucker and terminates 

 at the level of the bottom of the hollow of the sucker. The 

 main canal re-crosses the base of the scolex horizontally, 

 internal to and parallel to its first horizontal portion, but 

 external to the dorsal canal, until it reaches the base of the 

 left ventral sucker. It then ascends the median side of the 

 left ventral sucker, almost to the mouth of the sucker, then 

 turns again, running parallel to its former course until the 

 base of the sucker is once more reached ; it ihen passes around 

 the external surface of the base of the sucker, forming a few 

 spiral loops, until the outer lateral angle of the left suckers 

 is reached. It then ascends the outer lateral angle, giving off 

 a short blind branch towards the dorsal sucker at the level 

 of the nerve commissure. Arrived near the summit of the 

 scolex, it bends over and runs down the inner lateral angle of 

 the left sucker until the level of the cross nerve commissure 

 is reached ; here it bends inwards, and then upwards past the 

 nerve commissure, running ventral to and parallel to the 

 doi'sal canal until the apex of the scolex is reached. Here it 

 bends over dorsally and fuses with (or is continued into) the 

 dorsal canal. At the point of junction of the two canals the 

 commissure connecting the right and left halves of the 

 excretory canal system inserts. The dorsal canal is straight 

 throughout its entire length. 



The right ventral canal runs in a similar manner, at fii'st 

 ventral to and parallel to the right dorsal canal (fig. 6). 

 Near the base of the suckers it also bends over dorsally, and, 

 passing the dorsal canal externally, runs horizontally to the 

 base of the right dorsal sucker, following the outer face 

 of the sucker, which it ascends almost to its mouth, 

 veering during- this ascent more and more to the right. 



