MORPHOLOGY OF THE PEDIPALPI. 27 



tubes wMch lie side by side near the middle line, reaching as far 

 back as the eightb free segment. In the third and fourth free 

 segments they become narrowed into short vasa deferentia, 

 which open into the enormous seminal vesicles situated one on 

 each side of the first segment (fig. 8). These seminal vesicles 

 open in the middle into what may be termed the genital vestibule, 

 which runs straight back to open to the exterior at the posterior 

 edge of the genital plate. The dorsal wall of the posterior part 

 of this genital vestibule is formed by the median anterior process 

 of the third segment. Each of the seminal vesicles contains two 

 hard brown structures in the form of curved grooved rods. One 

 pair of these rods is united in a plate-like expansion in the 

 middle line. The other pair seem to be independent of each 

 other. No muscles could be found in connection with these 

 structures, and their function — except in so far as they serve to 

 keep the seminal vesicles dilated — is not evident. The walls of 

 the genital vestibule are strengthened by two curved, chitinous 

 bars (fig. 8, cl), which seem independent of the genital plate, 

 though coming into close contact with its inturned margin at 

 their posterior ends. A small ring of chitin (PI. III. fig. 8, e^) 

 also lies in the dorsal wall of the vestibule in front of the median 

 anterior process of the third segment. 



Underneath the testes, underneath even the nerve-cord, lies, 

 in the middle line, the right sac of the stinh-gland (fig. 6). It is 

 in contact on the ventral side with the body- wall and reaches 

 forward as far as the fourth segment, and the width is about 

 half tliat of the space between the dorso-ventral muscles. Traced 

 backwards, it narrows considerably in the tail-segments, and 

 passing to the right of the rectum opens close to the middle line 

 between the anus and the base of the telson. The walls of this 

 sac are thin and translucent, and are thickened by a number of 

 longitudinal white strands, which are due to the internal wall of 

 the sac being folded into complex longitudinal ridges (fig. 6 a). 

 These ridges suggest that the walls of the sac secrete the odorous 

 fluid ; but the free surface is covered by a well-marked cuticle 

 which is very impervious to staining fluids, and one would sup- 

 pose equally so to secretions. The left sac of the stink-gland 

 lies outside the left dorso-ventral muscles, and the narrow pos- 

 terior end passes to the left of the rectum to open close to the 

 aperture of the right one. It does not reach so far forward as 

 the right one, but ends in the middle of the fifth segment. The 



