STUDIES OX THE ECTOPARASITIC TEEMATODES OF JAPAX. 25 



investing membrane of the body makes a fold filled with connective 

 tissug within, and forms a marginal membrane (PL XII, fig. 4). 



Strong bundles of muscular fibres are attached to each sucker. 

 The principal bundles are, as may be seen in fig. 4, PI. XII, three in 

 number, and are attached one to the inner margin of an inner quad- 

 rant, another to its outer corner, and the third to the central part of the 

 T-shaped chitinous piece. The individual fibres that constitute these 

 bundles are very large. The larger part of the bundles of each sucker 

 are merged in a single bundle at a short distance from it, and the 

 bundle thus formed traverses the axis of the pedicel of the sucker, 

 when such is present ; but a small portion forms one or more bundles 

 which connect the suckers with one another. I have represented this 

 connection among the suckers as I have observed it in Diclid. sessilis 

 in fig. 5, PI. X. 



In Hexacotyle, there are four pairs of posterior suckers, and these 

 are arranged on each side of the median line in a line parallel with 

 the posterior border of the body. The median pair of all is, however, 

 very much smaller than the others, and has been entirely overlooked by 

 some naturalists ; but it has exactly the same structure as the other 

 pairs. Each sucker is shaped like a thick but very shallow, elliptical 

 saucer (PI. XII, fig. 7), Avith its longer axis directed at a right angle 

 to the posterior border of the body, and is provided with three 

 chitinous pieces imbedded in the substance of its wall, which consists, 

 as in the cases already described, of prismatic, refractive fibres closely 

 pressed against one another. The positions of these chitinous pieces 

 are represented in figs. 1 & 4, PL XIII; and in figs. 3 & 6 each 

 piece has been separately drawn, so that any detailed description of 

 them is, I believe, unnecessary. It is to be remarked, however, that 

 in both the figures, a represents the piece at the anterior end of the 

 sucker, c that at the posterior end, and b the central piece, and that 



