532 EDITH M. PRATT. 



The mesogloea is fairly dense owing to the presence of numerous large spicules, it is 

 less abundant than in the soft, fleshy species. 



The interesting features of the species are: (1) the erect arborescent form of the colony 

 (fig. 33); (2) the presence of numerous very large tuberculate spicules; (3) the absence of 

 siphonozooids ; (4) the well-marked character of the zooids, the mesenteries and their filaments 

 large compared with many other species ; (5) the comparatively feeble development of the 

 superficial and internal canal systems; (6) zoochlorellae present but not in considerable 

 numbers. 



V. THE RELATIONS OF THE ABOVE GENERA. 



Sclerophytum differs from Alcyonium in (1) the form and size of the spicules; (2) the 

 small size of the zooids; (3) the occurrence of dimorphism in many species; (4) the presence 

 of a special supei-ficial canal system ; (5) the small size or complete absence of ventral and 

 lateral mesenterial filaments. These important points of difference indicate a very distant 

 relationship between Sclerophytum and Alcyonium. 



A study of Table II. shows that while specimens of Sclerophytum and Lohophytum may 

 be similar in outward form, yet there are many striking points of difference in their internal 

 anatomy. The general anatomy of Lohophytum, however, is very similar in many respects 

 to that of Sarcophytum, with which it appears to be closely allied. 



Some of the important anatomical points of difference between Sclerophytum and the 

 two genera Sarcophytum and Lohophytum are: (1) the presence in Sclerophytum of more 

 than one row of pinnules on the tentacles; (2) the ventral and lateral mesenterial filaments 

 are always very feebly marked (but are absent in Sc. gardineri) ; (3) the presence of a special 

 superficial canal system ; (4) the absence of dimorjihism in some of the species. In all these 

 respects Sclerophytum approaches the genus Xenia. The following diagram suggests the 

 probable relationship between the four genera and Alcyonium. 



Common Ancestor 



I 



Sarcophytum Lobophytum Sclerophytum Xenia Alcyonium 



Mr Gardiner has given me the following note of the distribution of the genera Sarco- 

 phytum, Lohophytum, and Sclerophytum in the Maldives : — " They are found on nearly every 

 reef in the Maldives but are most common on the reefs which fringe the passages into 

 atolls. Under no circumstances are they ever found covering great areas, as Saville Kent 

 says is the case with Sarcophytum on the Great Barrier Reef of Australia. They do not 

 generally occur on shoals in the lagoonlets of secondary atolls (vein of faro), nor are they 

 found on any reef more than 100 — 1.50 yds. from its outer edge. In the more enclosed 

 atolls such as Goifurfehendu, Addu, Kolumadulu, and Haddumati, these genera are scarce, 

 only small colonies being found on the reefs arising within their lagoons. 



" The genera are common on the reefs of Hulule faro, Male Atoll. They live very 

 abundantly on the outside part of the west reef and form large spreading masses. On the 



