198 Records of the Indian Museum. [Vol.. X, 



which ends in the centre of the surface of the atrial bulb. In 

 this situation it joins the penis, a short, protrusible and mus- 

 cular tube which curves outward and to the right, and then 

 inward and backward to open into the cavity of the genital atrium 

 (Text-fig. 3 pe. and PL xxviii, figs. 9 and 10 pe.). This cavity is 

 enclosed in a muscular bulb (PI. xxvi, fig. i. PI. xxviii, g, 10 and 

 12. Text fig. 3 at. b.) and is divided by a diaphragm into a dorsal 

 male atrium and a flattened ventral female atrium. The male 

 atrium opens into the female atrium, and this in turn opens 

 to the exterior through the atrial pore. The penis projects 

 freely into the cavity of the male atrium. (PL xxviii, fig. 9 pe. i). 

 The diaphragm is armed with a circle of forty spines which when 

 viewed from the ventral surface appear to be straight truncated 

 rods with recurved fine points (text-fig. 2) but when looked at 

 from the side are seen to be S-shaped hooks (PL xxviii, fig. n) 

 sharp-pointed at the projecting extremity, and having a raised 



rem/,. 



Fig. 3. — -Diagram to explain the action of the atrial spines .'incl the \al\ular 

 action of the diaphragm on protrusion of the penis. See text. 



point on the outer aspect at the junction of the basal and median 

 thirds for the attachment of muscle fibres. The penis can 

 doubtless be extruded through the atrial pore and would carry 

 the diaphragm along with it. This protrusion would separate 

 the points of the hooks and the circlet would embed itself firmly 

 in any tissues with which it came into contact (text-fig. 3). 

 Self-impregnation would be prevented by the impaction of the 

 cone formed by the protruded diaphragm in the atrial pore, the 

 female atrium being closed completely during the protrusion of 

 the penis. 



The female organs. — (Text-figure 2). The ovary (PL xxvi, fig. i 

 and PL xxix, figs. 14-16 ov.) is situated ry mm. from the anterior 

 extremity. It is a curved sausage-shaped organ, the curve forming 

 all but a complete circle. The fundus is somewhat bulbous. The 

 ovary leads into the oviduct, a narrow canal which runs forward 

 to the uterus (PL xxix, figs. 14 and 15 od.). The latter organ 



