44 S. GOTO, 



In Onchocotyle, the hooks are situated near the extremity of the 

 caudal appendage, between the pair of small suckers already described, 

 on the morphologically ventral side (PI. X\^, figs. 1 and 2). They 

 are wholly solid, and are Hke a fishing hook in shape ; but the basal 

 end is divided into two processes, one of which bears again a rounded 

 process (PI. XV, fig. 5). I have not been able to demonstrate any 

 muscular fibres attached to the hooks. 



In Tristomum, the hooks are situated at the extremities of the 

 posterior border of the central polygon of the posterior sucker, and are 

 provided each with a strong muscle formed by the direct continuations of 

 the longitudinal fibres of the body. They are,unlike the hooks of most 

 other genera, more or less straight (Pis. XX, XXIII, XXIV, XXV). 



In Calicotyle and Monocotijle, the hooks are situated in the 

 posterior radial spokes of the posterior sucker on both sides of the 

 median line of the body, and project free over the surface of the invest- 

 ing membrane at the margin of the sucker (PI. XVII, figs. 1 and 2 ; 

 PL XIX, fig. 1). They are strongly recurved in both genera. 



In Hexacotyle and Octoc. minor, there are two pairs of hooks, of 

 which one is much smaller than the other. They are situated at the 

 posterior end of the body, on both sides of the median line, and 

 between the innermost pair of suckers in Hexacotyle. In both cases 

 the smaller pair of hooks lie nearer the median line (PL IX, fig. 7 ; 

 PL XIII, figs. 1, 2, 4, & 5). 



Finally in Epibdella, there are three pairs of hooks. They are 

 situated on the ventral side of the posterior sucker, and the three pairs 

 are arranged one behind the other ; the most posterior pair being close 

 to the margin of the sucker. Each hook is provided with a strong 

 bundle of muscular fibres. 



The genera Microcotyle, Axine, and Dididopliora are, so far as I 

 haye observed, entirely destitute of hooks. 



