.REPORT ON THE HOLOTHURIOIDEA. 77 



dorsal portion of the circular vessel, and passes upwards and backwards to the body-wall, 



where, surrounded by a thick layer of connective tissue, it joins the medio-dorsal line 

 about 30 mm. behind the tentacles. When the tube reaches the perisoma it gives off 

 four to five, sometimes even as many as nine (PL XXXVIII. fig. 9), very narrow 

 branches, which pierce the body-wall and open externally each at the top of a minute 

 papilla. These papilla?, measuring from 2 to 3 mm. in length, are closely crowded together 

 at the base of the genital process, which is situated anteriorly in the medio-dorsal line, and 

 which is in connection with the efferent duct of the reproductive organ. The position of 

 those papdhe is various ; sometimes they are placed immediately in front of the genital 

 process, sometimes they form a semicircle along one side of it. Through the openings 

 in the free ends of the papillae the ambulacral system communicates with the surrounding 

 medium. The deposits of the madreporic canal consist partly of scattered more or less 

 aggregated, minute, slender, straight or curved, branched or unbranched irregular rods, 

 partly of a few irregular wheels differing more or less from those in the integument, 

 and finally of a few irregular perforated plates in the form of a network. 



The posterior portion of the digestive tract is generally slightly enlarged, except- 

 ing in some individuals dredged at Station 147 ; two of these possess a large cloaca, 

 which in one of them gives off a caecal prolongation on the left side ; in two other 

 specimens from the same locality the cloaca is almost imperceptible. The parietes of 

 the alimentary canal as well as the walls of the pseudhaemal vessels contain calcareous 

 deposits in the form of spicula (PI. XXXVI. fig. 3). The reproductive organ (PI. 

 XLIII. fig. 4, g) consists of two large fascicles made up of bundles of small oval caeca 

 (PL XLVI. figs. 2 and 3), one fascicle on each side of the dorsal mesentery ; its efferent 

 duct opens externally by a pore situated on the top of the aforesaid process which has its 

 place in the medio-dorsal line and reaches a length of 11 mm., and a diameter, at 

 the base, of 2*5 mm. This genital process has sometimes a branch projecting from its 

 side, the efferent duct thus having two apertures (PL XXXVIII. fig. 9) ; sometimes the 

 top of the process is divided into four small branches, only two of which seem to com- 

 municate with the efferent duct (PL XXXVII. fig. 5). I have only once met with an 

 individual provided with two equally large processes side by side, and in which conse- 

 quently the common duct must have divided while piercing the perisoma. Thus it is of 

 importance to remember that both the reproductive organ and the madreporic canal are 

 subject to considerable variations in their manner of terminating. 



As the above description is taken from the individuals which we're obtained at 

 Station 300, it is necessary to point out the more or less important characters 

 which distinguish the specimens brought home from other stations. The individual 

 from Station 232 was in such an incomplete state that no close examination is 

 possible ; it is only 25 mm. long, and has thirteen developed tentacles and rudiments 

 of a fourteenth ; it is most probable that this form is a distinct species from Lcetmogone 



