182 J. H. ASHWORTH. 



of working out the arrangement of the canals of the colony. As the 

 investigation proceeded the preservation of the colony was found to be 

 so exceptionally perfect that it seemed desirable to make a study of its 

 histology, and as several new and interesting points were early 

 observed I finally decided to work out in detail the complete anatomy 

 and histology of the colony. Although many authors have described 

 the external characters of various species of Xenia, few have paid any 

 attention to their internal structure. Bourne (1895) has referred to 

 the canal system, the mesogloea, and the distribution of spicules in 

 two species of Xenia, and in Heteroxenia Elizabeths, and Kolliker 

 (1874) described the anatomy of his new Heteroxenia Elizabeths as far 

 as its very imperfect preservation would permit. These two accounts 

 contain practically the whole of our knowledge of the internal struc- 

 ture of these two genera, and hence, when the beautiful preservation 

 of this colony of Xenia from Talisse was apparent, there was a strong- 

 inducement to attempt a more complete account of its detailed 

 anatomy and histology. 



The work has been carried on during the past two years in the 

 zoological laboratories of the Owens College. My best thanks are due 

 to Professor Hickson for the beautifully preserved specimen upon 

 which most of my work has been done, and for advice and criticism 

 given during the progress of the work. I am also indebted to Pro 

 fessor Lankester for a specimen of Heteroxenia Elizabethan, to Mr. J. S. 

 Gardiner for a specimen of Xenia from Rotuma, and to Dr. Arthur 

 Willey for fourteen specimens of Xenia from various reefs in the 

 Pacific. 



External Characters op the Colony (PI. XVI IT.). 



The Xeniidce are distinguished from all other Alcyonaria by their 

 soft, fleshy consistency and non-retractile polyps. The former character 

 is due to the fact that their spicules are very minute rounded or oval 

 discs, which have an organic basis impregnated with only a small 

 quantity of calcium carbonate. 



This colony arises from a single stem, which is slightly expanded at its 

 point of attachment to the rock, and measures about 15 mm. in diameter 

 at that point. This basal portion is very short and thick, and supports 

 four main stems, all of which divide into two or more, producing 

 altogether thirteen stems or branches ranging in length from about 



