9(3 S. GOTO. 



this last piece is imbedded in the wall of the sucker with its longer 

 axis coincidins: with the minor axis of the sucker. The substance of 

 the wall is bounded, as in other genera, both towards the mesenchyma 

 and the exterior by a cuticular membrane, except in the central pa-rt 

 where the chitinous piece is imbedded, and where this is in direct 

 contact with the mesenchyma. A strong bundle of muscular fibres, 

 which are direct continuations of the longitudinal fibres of the body, 

 are attached to each of the chitinous pieces of the sucker (PI. XII, 

 fig. 7). 



Onchocotyle — The position and structure of the suckers are 

 somewhat peculiar in this genus. 



Anterior sucker — ^An anterior sucker is distinctly present, although 

 some writers have denied the fact, and is situated around the mouth- 

 cavity, and presents some resemblances of structure, to that of the 

 distomes. In cross-section, it is elliptical in outline, and is seen to 

 occupy nearly the whole of this region of the body, merely leaving a 

 small portion of mesenchyma in the lateral parts (PI. XV, fig. 4). 

 The ventral half is much smaller than the dorsal half, just as in the 

 distomes (PI. XV, fig. 3). The substance of the sucker consists 

 of connective tissue interspersed with nuclei, some of which are 

 surrounded by scanty masses of granular protoplasm, and of muscular 

 fibres, most of which are very fine, and, radially traversing the con- 

 nective tissue, are attached to the basement membrane which separates 

 the substance of the sucker from the investing membrane of the body. 

 Besides these radial fibres, strong muscular fibres which act as 

 sphincters are present in the foremost part of the dorsal half qf 

 the sucker (PL XV, fig. 3, sph.) 



Posterior suclters — These are eight in number arranged in four 

 pairs, one of which is, however, very different both in structure 

 and position fi-om the others. The latter are arranged in a horse- 



