122 
ME. H. N. MOSELEY ON THE 
Carbonate of lime 94-226 
Phosphates and fluorides . . . 1-200 
Organic matter 4 - 574 
Mr. S. P. Sharples* found the corallum of Millepora alcicornis to consist of: — 
Carbonate of lime 9 7 -46 
Phosphate of lime 0"27 
Water and organic matter . . . 2-4 
There is no marked difference between these results and those obtained from ordinary 
corals. 
Structure of the Soft Parts. 
Structure of the Zooids. — The calicles of the Millepora are occupied by two kinds of 
zooids. In each system of calicles the central larger one is occupied by a short and 
broad zooid provided with a mouth, whilst the surrounding smaller calicles lodge longer 
and more slender zooids which have no trace of mouth. A system of expanded zooids 
is shown in Plate 3. fig. 9, one of the mouthless zooids being omitted in the drawing 
in order to show the central mouthed one more clearly. 
The mouth-bearing zooids are much shorter and broader than the mouthless ones. 
They were not directly measured, but were estimated to be about -5 millim. in height. 
They are cylindrical in form, with a short conical hypostome, and four, five, or six ten- 
tacles arranged equidistantly in one whorl just below the short hypostome. The ten- 
tacles consist of a short, stout, cylindrical stem, with a spheroidal knob-like tip composed 
almost entirely of thread-cells. At the summit of the hypostome is the mouth, which 
in the living expanded animal has a conspicuous glistening white appearance — no doubt 
because light is strongly reflected by the large gastric cells which surround the aperture. 
The mouth-area is circular in outline (in M. alcicornis quadrangular sometimes), 
Plate 3. fig. 11, MZ. The circular area is occupied by a series of large, elongate, trans- 
parent gastric cells, which are disposed in a radiating manner around the centre of the 
area. The actual mouth-orifice takes the form either of a threefold or cruciform slit 
between the gastric cells. The gastric cells (Plate 3. fig. 15) are elongate, irregularly 
cylindrical in form, and transparent and bladder-like in appearance, and without any trace 
of a nucleus. They line the internal cavity of the zooid for at least one third of its length, 
but to what extent exactly was not ascertained. They appear to be closely similar to 
the pyriform cells described by Allman, and figured by him as occurring in Gemmaria 
implexa f . They are here termed gastric, because the fact that they occur only in the 
mouthed zooids seems to render it probable that they exercise a digestive function. 
The mouthless zooids are long and slender in comparison with the mouthed ones. They 
differ very much in length, as will be seen from the figure; the longest of them 
measure about 1-| millim. in length. They are cylindrical in form, tapering towards 
•* 4 Corals and Coral Islands,’ by J. D. Dana (London, 1872), p. 105. 
t Allman, 4 Gymnoblastic and Tubularian Hydroids,’ pi. viii. fig. 5. 
