120 PROF. A. DENDY AND MK. E. HINDLE : ADDITIONS TO 



to radiate from the ganglion, which also lies immediately beneath the 

 epidermis. 



(ii.) " Taste-pits^' (fig. 3). — These are common in the epithelium o£ the 

 buccal region. Each consists of an ectodermal pit which is lined by very 

 regular, concentrically-arranged, columnar cells. As the nuclei o£ these cells 

 are situated at their bases, the whole organ appears as a conspicuous sub- 

 spheroid body in the ectoderm^ with a diameter of 0*031 mm. In the centre 

 of this body is a core of sensory cells (c.) bearing short cilia which project 

 into the lumen of the pit. A nerve («.), arising from the nerve-layer of 

 the integument, supplies these sensory cells. From the structure of these cells 

 it is probable that they are gustatory in function, and their restriction to the 

 buccal region also supports this view. The ordinary columnar cells of the 

 pit appear to serve merely as a support for the sensory cells of the core. 



These organs resemble the ciliated pits described in Syncvpta by Hamann *. 



(iii.) Otocysts (fig. 2, fig. 23, ot'). — There are five pairs of otocysts, each 

 pair being situated on the pharynx right and left of the corresponding- 

 radial nerve shortly after its commencement. Each is supplied by a 

 branch from its corresponding nerve. The structure of the otocyst appears 

 to difi'er somewhat from that of Synapta, as figured by Semon f. In 

 transverse sections the sac appears triangular with somewhat convex sides 

 and rounded angles. The length of the otocyst is 0*084 mm. and breadth 

 0*056 mm. Its wall is formed by a single layer of cells which on the side 

 nearer to the radial nerve are of approximately equal size and cubical in 

 shape. The middle of the wall remote from the radial nerve appears as 

 a thin membrane (fig. 2, d.) and is composed of flattened cells. The nerve 

 enters at one corner of the triangle, and here the lining cells of the otocyst 

 are more elongated than in any other part. The nerve appears to separate 

 into fibres which form a layer round the outside of the otocyst. The sac 

 contains numerous rounded otoliths (ot.) of varying size. 



Repi'oductive Organs. — The sexes are distinct. In both male and female the 

 gonads (fig. 16, g.) consist of two bunches of sparingly-branched cseca, 

 arranged right and left of the dorsal mesentery in the anterior third of the 

 body-cavity. The left bunch is larger than the right. About the level of 

 the ring-canal they unite in a slender genital duct (fig. 17, g.d.) running 

 forwards in the dorsal mesentery to open mid-dorsally between, and internal 

 to, the two dorsal tentacles. 



" Ciliated Funnels " (figs. 25-29).— Peculiar funnel-shaped organs occur 

 commonly on the mesentery and the longitudinal muscle-bands ; in the former 

 position they are almost invariably clustered together, in little groups of 



* Hamann, Beitiage zur Histologie der Echinodermen. Die Holotliurien, p. 22. 

 t Semon, Beitrage zur NaturgescMclite der Synaptiden des Mittelmeeres. 2. Mittheilung. 

 Mittheilungen aus der Zoologischen Station zu Neapel, vol. vii. pi. 15. tig. 8. 



