THK STKUCTURE OF XENIA HIOKSONI. 253 



do not occur among the cells which form the siphonoglyph 

 (PI. 25, fig. 10). Secreliug cells have not hitherto been noticed 

 in the storaodaeum of the Alcyonaria (Ashworth^ 1898), 



These goblet-cells of the stomodseum are the only secreting 

 cells connected with the digestive cavity, as the six thick short 

 ventral and lateral mesenterial filaments, which bear the gland- 

 cells in other Alcyonaria, are absent in all polyps of this 

 Xenia (see Woodcut, p. 252). Only the dorsal mesenteries 

 possess thickened edges, forming two mesenterial filaments 

 {D.M.F.) which have a similar course and structure to those 

 of Alcyonium. The free edge of the ventral and lateral 

 mesenteries is only very slightly thickened, and the thickening 

 is due entirely to the greater amount of mesogloea present at 

 the edge of the mesentery. The cells which cover the edge 

 differ in no way from those which cover the remaining portions 

 of the mesentery. 



New points in the anatomy of this Xenia are the presence 

 of gland-cells in the stomodseum, and the absence of the six 

 ventral and lateral mesenterial filaments usually present in the 

 polyps of the Alcyonaria. Wilson (in Kophobelemnon, 

 188-1) and Hickson (in Alcyonium, 1895) have shown that 

 these mesenterial filaments bear the cells which produce the 

 digestive secretion. I would suggest that the absence of these 

 filaments in this Xenia is correlated with the presence of gland- 

 cells in the stomodseum, and that the latter, judging from 

 their appearance and position, perform some digestive function. 

 As mentioned above, the cells are most abundant on the ventro- 

 lateral walls of the stomodseum, near the siphonoglyph. As 

 the flagella of the siphonoglyph create an inward current of 

 sea water carrying food particles, which passes along the 

 ventral groove, the greater abundance of secreting cells 

 in the walls abutting on this groove is suggestive of the 

 digestive function of the secretion, which can readily be poured 

 out on to the ingoing food particles. 



The siphonozooids which occur in some other Alcyonacea 

 (e.g. Sarcophyton) and in Pennatulids are the only re- 

 Qorded examples of polyps in which the ventral and lateral 



