THE ANATOMY OF THE MADREPOEAKIA. 421 



retractor muscles. The reason that their occurrence has been 

 hitherto overlooked is, that the mesoglcea is stained only when 

 the colouring matter, whether carmine or hsematoxylin, is 

 strong and diffuse ; but I have now detected them in Flabellum 

 (2 sp.), Amphihelia, Seriatopora (2 sp.), Pocillopora (2 sp.), 

 Stephanophyllia, and Sphenotrochus : and Bourne has recently 

 described their occurrence in Mussa (' Quart. Journ. Micr. Sci./ 

 xxviii). 



Dr. von Heider, of Graz, who was the first to call attention 

 to the existence of calicoblasts, describes in a recent account 

 of Dendrophyllia ('Zeitschr.wiss. Zool.,' xliv) a structure which 

 he regards as calicoblastic, in terms which apply exactly to a 

 transverse section of these processes. His figures (pi. xxxi, 

 figs. 9, 11) do not, however, clearly show whether the two 

 structures are identical or not, though it seems probable that 

 they are so, and that what he describes as needles of calcium 

 carbonate inside the " cells," are the lines of lamination (cf. 

 Bourne, 'Quart. Journ. Micr. Sci.,' xxviii, p. 25). It should 

 be noticed, on the other hand, that he explicitly states 

 that, in some at least of these so-called cells, a nucleus was 

 present. 



In Stephanophyllia these processes are to be found at the 

 base of each mesentery, and form a band running down the 

 sides of the radial trabecula to which the mesentery is attached; 

 but their structure is not different from those occurring in 

 Flabellum and other forms, and their position a natural con- 

 sequence of the different position of the theca (fig. 6). 



Figures and description of the corallum may be found in 

 Moseley, " Chall." Rep. Zool., ii, p. 198, pis. iv, xiii, xvi. 



Sphenotrochus rubescens (figs. 9 — 12). 



A study of some fragments of this coral, entrusted to me by 

 Professor Moseley, has produced one or two points of con- 

 siderable interest, though, as with Stephanophyllia, the account 

 is necessarily incomplete. 



The corallum is not unlike that of Flabellum, near which 



