Angular Sea-Cucumher. 151 



buliforni organs developed upon their mesentei'ic membranes, the 

 functions of which may be supposed to be identical with those of 

 the org-ans they replace. With the absence of lungs the pecu- 

 liarity of monoeciousness or hermaphroditism is correlated in the 

 Holothurioidea. On the right side in this Preparation is seen the 

 generative gland, which consists of two bilaterally symmetrical 

 fascicles of coeca, attached on either side of a thickened portion of 

 the dorsal inter-radially placed mesentery. A single efferent duct, 

 under which a slip of blue paper is passed, passes along in this 

 mesentery to open inside the circle of oral tentacles, at the anterior 

 end of the dorsal inter- radial ossicle ; and it is seen just posteriorly 

 to it in the interval between the madreporic canal, which is also in 

 relation with the dorsal mesentery, and one of the retractor muscles 

 which is passing to be attached to the radial ossicle on its right. 



Tlie structural arrangements of the Dendrochirotae, as illustrated by 

 this Preparation, differ in the following particulars from those of the 

 Aspidochirotae, as illustrated in the Hunterian Catalogue, vol. i. pi. iii., 

 vol. iv. pi. xlix. Their arborescent tentacles are carried upon a cylin- 

 driform prolongation of the body, which is differentiated from the part 

 which carries the five rows of ambulacral feet, and thus comes to be 

 not wholly unlike the proboscis of certain marine Annelids ; special 

 retractor muscles are developed in correlation with this apparatus ; a 

 muscular stomach is more commonly found in them than in the Aspi- 

 dochii'otae ; their respiratory trees are less developed in length and 

 complexity, and the pseud-haemal system does not come into relation 

 with them ; the ' Cuvierian organs,' certain structures developed upon 

 the stem of the respiratory trees or upon the cloaca, and of various 

 shapes, appear to be very commonly wanting in them, as are also the 

 ampullae of the ambulaci'al tentacles nearly invariably, though their 

 Polian vesicles ar£ more prominently developed than those of the Aspi- 

 dochirotae. In the periphei'al part of the water-vascular system, the 

 Dendrochirotae differ from the Aspidochirotae, in never having suckers 

 or calcareous disks developed upon their tentacles : these structures 

 may be absent also in the feet of the ambulacral, and especially of the 

 dorsal ambulacral, rows, but they may be both present there. 



The generative gland is bilaterally symmetrical in the Dendrochirotae, 

 consisting of two fascicles of short and non-bifid coeca, attached on either 

 side of a thickened portion of the inter-radially attached dorsal me- 

 sentery, and communicating with a single efferent duct of great length, 



