186 J. H. ASHW0RTH. 



support the polyps in their natural position when the colony is 

 removed from the spirit. The spicules are round or oval discs 

 measuring "012 mm. to "022 mm. in length, '006 mm. to "013 mm. in 

 width, and about '004 mm. in thickness. They are numerous in the 

 ectoderm of the stem and of the body of the polyp, but are practically 

 absent from the tentacles and pinnules. 



Round the edge of the umbellate summit of each stem are a few 

 buds or young polyps in early stages of development. The specimen is 

 light brown in colour (in spirit). 



Habitat. — The reefs of Talisse Island, North Celebes. 



This species appear to differ from most, if not all other species of 

 Xenia in the absence of spicules from the tentacles and pinnules. In 

 general form of the colony this specimen most resembles X. umbellata, 

 Savigny, but it differs from the latter in possessing smaller polyps, 

 with much shorter and stouter pinnules, which do not leave the axis 

 of the tentacle free along its whole length (cf. Klunzinger, 1877, PL 3, 

 Fig. 3a). 



General Anatomy. 



Stomodcemn and Mesenterial Filaments. — In the centre of the oral 

 disc of each polyp there is a funnel-shaped depression about one-third 

 of a millimetre in depth leading to the mouth. This depression is 

 formed by partial contraction of the oral disc ; if the polyp were fully 

 expanded this depression would not exist, but the mouth opening would 

 be level with the oral disc. The mouth {Mo.) leads into the stomo- 

 dseum (St.), which is T8 mm. to 2*2 mm. long. The stomodseum is 

 long compared with the length of the free portion of the polyp, and in 

 longitudinal section presents a striking appearance, running down, as 

 it does, so far into the coelenteron. The stomodseum is oval in trans- 

 verse section, being somewhat flattened from side to side. It has a 

 well-marked ventral groove or siphonoglyph (Si.), the cells of the lower 

 third of which bear long flagella (F.). The groove is not as well 

 marked in the upper as in the lower portion of the stomodaeum, and is 

 scarcely discernible at the mouth opening. The columnar epithelial 

 cells forming the siphonoglyph are, as is usual, longer than those of 

 the rest of the stomodseum, and these cells bear very long flagella 

 ("07 mm.), which in some examples extend almost to the centre of the 

 cavity of the stomodseum. The epithelium of the rest of the stomo- 



