94 S. GOTO. 



on its external, concave face bears a number of recurved, chitinous 

 spines, which together constitute the chitinous penis. Each of these 

 hooks consists of a mound-shaped basal portion and a hollow, spinous 

 distal portion. The substance of the penis bulbs has the same his- 

 tological structure as that in Diclidophora. 



Calicotyle — In this genus the connective-tissue penis is a some- 

 what kidney-shaped body formed of fibrous tissue containing nuclei, 

 separated however, from the surrounding mesenchyina by a distinct 

 membrane, except at one place where the fibres of the surrounding 

 mesenchyma are seen to be directly continuous with those of the penis 

 (PL XIX, fig. 11). The. penis has one end smaller than the other, 

 and in its natural state, is placed so that its smaller end occupies 

 a more dorsal position in the body than the other (PI. XIX, figs. 7 

 & 11). Its smaller end is directly continued into the chitinous penis, 

 which is an exceedingly long, hollow tube with obliquely cut end, 

 aiid is twice bent on itself in such a way that the middle portion 

 crosses the middle of the distal portion (PL XIX, fig. 10), As 

 ju-st side, its base is directly applied to the outer end of the con- 

 nective-tissue penis (PL XIX, fig. 11); and it lies in a tubular 

 cavity just large enough to receive it, the direct continuation of the 

 genital atrium. 



Monocotyle — The connective-tissue penis is in this genus a 

 somewhat pear-shaped organ attached to the body by its smaller end 

 at the bottom of the genital atrium (PL XVIII, fig. 3), and is perfo- 

 rated by a canal. The substance of the penis consists of fibres which 

 are of similar general appearance to those of the suckers of Micro- 

 cot yle and some other genera, but are finer and stain better with 

 haematoxylin. They are arranged perpendicularly to the surface of 

 the penis, and at its base are seen to be directly continued into the 

 mesenchyma of the body, which, however, consists in this region of a 



