THE ANATOMY OF THE MADREPORARIA. 417 
theca) from which the septa spring vertically upwards, and 
which is marked on the lower surface by costz corresponding 
to the septa. Itis generally classed with the Fungida; since 
the researches of Bourne (‘ Quart. Journ. Micr. Sci.,’ xxxvii, p. 
293), however, we know that Fungia is a true Perforate coral, 
which may perhaps be allied to the Eupsammide (‘ Anat. 
Madr.,” iv), and which differs mainly from other Perforata in 
constructing a flattened discoidal theca, instead of the more 
usual vertical cylindrical form. Bathyactis, on the other hand, 
belongs more properly to the Imperforata, the theca consisting 
of asolid plate, with the exception of certain specimens 
instanced by Moseley (Chall. Rep. Zool., ii; ‘ Deep Sea Corals,’ 
p. 186) in which apertures in the peripheral region of the 
theca were obviously due to an insufficient supply of calcium 
carbonate. 
Sections of a decalcified specimen showed twenty-four ecto- 
ceelic and twenty-four entoccelic septa; twenty-four pairs of 
alternately longer and shorter mesenteries, of which two pairs 
at opposite ends of a diameter were the directives. The basal 
tissues do not consist merely of ectoderm and mesoglea (cf. 
Moseley, 1. c., p. 189), but are identical with the extra-thecal 
tissues of an ordinary Imperforate, such as Lophohelia or 
Mussa (fig. 10). It is therefore not the case that these tissues 
are the original basal body wall of the embryo (‘ Anat. Madr.,”’ 
i), this tissue undergoing presumbly the usual transformation 
into the calicoblastic layers of the adult; but Bathyactis bears 
the same relation to the Imperforata as does Fungia to the 
Perforata, in forming a discoidal theca by continuous hori- 
zontal growth instead of a cylindrical one by vertical addi- 
tions. 
Figures and a description of the corallum will be found in 
Professor Moseley’s report on Corals (Chall. Rep. Zool., vol: ii, 
p- 185). 
AppENDUM.—Since the above paper was in type, I have had under obser- 
vation in the Plymouth Laboratory of the Marine Biological Association a 
living specimen of Caryophyllia about 4 mm. high, which is absolutely devoid 
of extrathecal soft tissues. The discrepancy between my observations and 
