146 PROE. p. M. DUNCAN ON THE 



it contribute to the basal wall before the septum has increased 

 much in height. 



The additions of new septa are made with growth of the coral 

 more and more remotely from the axis ; and they are possible 

 because of the divergence of the radially disposed larger septa. 



The Columella. — The columella is composed of lax trabeculee 

 crowded togetlier ; and it is a very low structure at the bottom 

 of the axial space. No additional structures are given to it by 

 the septa, and it rests upon a thick part of the wall ; and pro- 

 bably it is really the only part of the base which has not a 

 synapticular origin. 



Tlie Interlocular Spaces. — It is evident that the spaces in which 

 the soft parts are contained are very restricted. There is the 

 axial space bounded below by the columella, and it extends 

 between the septa only for a short distance. It is bounded up 

 to a certain height by synapticular ridges. Above the limits 

 of the ridges there are the interseptal loculi, wiiose base is 

 at the level of the upper synapticula. But the loculi are con- 

 tinued to the base of the corallum along the canals formed by 

 contiguous synapticular ridges and the septa they join together. 



The interseptal loculi are therefore not closed below perfectly ; 

 but this open condition is slight, and is diminished or destroyed 

 by growth. 



One might speculate upon the impossibility of the occurrence 

 of mesenteries, and wonder whether these forms are really corals. 



It is extremely probable that the peculiar shape of the base of 

 the Fungidse- relates to this communication between the yisceral 

 cavity and the outside*. 



Histology of Hard Pm'ts.^Tlhe microscopic appearances of 

 this Fungia, in sections tangential to the septa, and which neces- 

 sarily include large and small septa and synapticula, denote that, 

 whilst some synapticula are continuous with the septal structure, 

 others are not and are independent. When the section is rubbed 

 down thin enough for the employmeJit of an object-glass of 

 300 diameters, the septa show multitudes of dull and light 



* The species of Fungia examined and described here is a variety of Fungia 

 sciitaria, Lamk., from the Red Sea and Indian Ocean. It departs from the type 

 in the extreme minuteness of the ornamentation, the great niauber of septa 

 (although this may be accounted for by growth), and the larger spines on the 

 base. It seems to connect Fungia faumoten&is, Stutchbury, and F. scutaria, both 

 of them being members of the artificial group of genera classified by Milne- 

 Edwards and Jules Haime as Fimgim mhintcgrcE {oii. cit. \o\. iii. p. 16). 



