ON SOME PLYMOUTH HOLOTHURIANS. 231 



as a synonym of C. pentactes, most of the specimens of which he records 

 from Plymouth. 



It has been shown in the foregoing pages that the Plymouth species 

 called C. pentactes in 1892 is undoubtedly the same as Brady and Eobert- 

 son's C. saxicola. This species is, however, totally different from 

 C. elongata Diib. and Kor., as may indeed be gathered from the description 

 of this animal given by Diiben and Koren (14). Kemp (13) has recently 

 given a good description of the external characters and spiculation of 

 C. elongata Diib. and Kor. from Ireland. The Plymouth specimens agree 

 well with Kemp's description and with that given by Diiben and Koren 

 themselves. There is thus no doubt that C. elongata is a good species 

 and quite different from other Plymouth Cucumarians. 



Some of the specimens obtained have been kept under observation 

 alive for as long as nine months embedded in fine sand. In life the 

 posterior end of the body, " the tail," protrudes above the surface of the 



,-vwJL-, 



Fig. 11. — Drawing from life of the " tail " of Thijone raphanus protruding from the 

 sand (x 4). 



sand presumably for the purpose of respiration. (Comp. Fig. 11.) The 

 body is bent in a U- or S-shaped fashion as was observed in the freshly 

 caught animal. During the whole of the period these animals were kept 

 the tentacles have rarely been seen above the surface of the sand. 

 It is possible, therefore, that the animal feeds mainly by ingesting mud 

 or sand, as it is apparently much too sluggish to search actively for food. 

 The tentacles in this species are very short, as may be gathered from 

 Fig. 10, which is a drawing of a specimen narcotized by menthol. Int 

 this figure is well shown the double rows of tube-feet near the middle 

 of the body and the gradual passage into single rows towards both the 

 tapering ends of the body. 



It has already been noted that the gonadial tubes of this species are 

 numerous and cylindrical, resembling those of C. normani both in shape 

 and approximately in numbers. The retractors of the buccal mass are 

 extremely short and altogether poorly developed. 



The gonads of female specimens taken in June and July were found 

 to contain nearly ripe eggs ; in July, 1912, a specimen was obtained 



