120 
ME. H. N. MOSELEY ON THE 
notches in the summits of the walls of the ccenenchymal tubes and calicles, in order to 
place these cavities in communication with one another. In Favosites the calcareous 
tissue surrounded the transverse canals, and the perforations in the walls of the calicles 
were thus produced. 
If Favosites was an Alcyonarian, Chcetetes was of course also of that group. The 
genus Alveolites amongst the Tavositidse is peculiar for the possession of three tooth- 
like prominences as the only representatives of septa. One tooth, well developed, is 
situate inside the calicle ; on that side of each calicle which lies externally in the 
colony, and opposed to this on the tip of the calicle next the interior of the colony, are 
a pair of rudimentary teeth. This arrangement reminds us at once of the distinction 
of dorsal and ventral mesenterial interspaces in Alcyonarians, and the direction of all 
the “ Dorsalfacher ” in Sarcophyton and Heliopora towards the central axis of the 
colony. In Alveolites the two teeth seem to correspond to the “ Dorsalfach,” and the 
single one to the “ Ventralfach,” the two teeth having occupied the space devoid of 
retractor muscles. Kolliker describes a series of teeth as existing at the margin of the 
calicle in Menilla , which follow a constant law in their relation to the septa. When 
only one tooth is present it is opposite the “ Dorsalfach when three, one is opposite 
the “ Dorsalfach,” and the two others opposite the lateral “Ventralfach.” In Alveo- 
lites the one tooth is ventral instead of dorsal. In Syringopora the septa seem to be 
very much of the same nature as in Heliopora ; and in Heliopora, as already described, 
the tabulae are not merely transverse floors, but the bottoms of cups of hard tissue fitted 
inside the older tubes and calicles. In Syringopora this condition of the tabulae is 
much more marked, and the corallum appears as if formed of a series of calicles fitted 
one within another. 
A difficulty appears to arise from the peculiar mode of the development of the 
calicles by budding in Heliopora, the foldings of the walls of the calicles being due, to 
a considerable extent at least, to the formation of these walls from a circle of ccenen- 
chymal tubes. The septa are, however, not entirely formed in this way. It would of 
course be of great interest to see whether the primitive calicle, in the developing 
Heliopora colony, forms calcareous septa. 
Heliopora having so commonly twelve septa, and in conjunction with these eight 
mesenteries, it was at first thought that here some key would be found to the eluci- 
dation of the question of the relations of the tetrameral corals to the Hexactinians ; 
but no definite arrangement of the eight mesenteries to the twelve septa could be 
discovered. Ludwig and Pourtales have concluded that the tetrameral condition in the 
Rugosa is the result of a modification of an originally hexameral arrangement — that 
the Rugosa are, in fact, modifications of the Hexactinian type. Kunth, however, using 
similar methods, has come to an opposite conclusion. Now that it is known that an 
Alcyonarian exists which constructs a solid calcareous corallum, in histological structure 
scarcely, if at all, to be distinguished from that of many Madreporaria, and that this 
Alcyonarian also possesses marked calcareous septa, which septa show, notwithstanding 
