262 J. H. ASHWORTH. 



bedded iu a small mass of protoplasm (figs. 13 aud 14). In 

 all the specimens^ many hundreds iu number, which I have 

 examined, the spicule develops in a single cell with one nucleus. 

 I have not been able to find any examples which showed that 

 two cells or two nuclei were concerned in the formation of the 

 spicule (cf. V. Koch's account of the development of the 

 spicules of Clavularia prolifera, ' Morph. Jahrb./ vii, 

 p. 473, 1882). 



Mesenteries (PL 26). 

 Mesenterial Filaments. — The stomodseum leads into 

 the ccelenteron of the polyp, which is subdivided by the usual 

 eight mesenteries (PL 25, fig. 10) . Of these only the two dorsal 

 ones possess thickened edges or mesenterial filaments (PL 26, 

 fig. 19). The free edge of the remaining six mesenteries is 

 only very slightly thickened, this being due entirely to the 

 presence of a slightly greater amount of mesogloea near the 

 free edge of the mesentery. The cells which cover this 

 thickened portion differ in no way from those covering the 

 other parts of the mesentery (PL 26, fig. 20). The six ventral 

 and Literal mesenterial fihunents usually present in the polyps 

 of the Alcyonaria are not found in this genus. The dorsal 

 mesenterial filaments arise from the lower edge of the stomo- 

 dseum aud run in a sinuous course along the dorsal side of the 

 ccelenteron. In the primary polyps they may be traced to the 

 base of the colony. In transverse section the filament is 

 slightly bilobed, i. e. there is a groove (of slightly varying depth) 

 extending all the way down the middle of the free surface of 

 the filament (fig. 19). The cells on each side of this groove 

 bear long cilia ('0075 mm.). The dorsal mesenterial filaments 

 are quite typical, and agree well with the accounts given of 

 those of other Alcyonaria by Vk'^ilsou and Hickson. They are 

 probably ectodermic in origin, as they appear to be formed as 

 two downgrowths from the inner end of the stomodseum. The 

 cells of the filaments agree in structure with those of the 

 stomodaeum, being finely granular and non-vacuolated, and 

 differing markedly from the much vacuolated neighbouring 

 endoderm cells. 



