MR. H. N. MOSELEY ON THE STRUCTURE OF THE STYLASTERIDHD. 
441 
in the recent condition of the coral. They do not contain any form of zooicl. It is to 
be noted that in Pliobothrus tubulatus, a second species (Pourtales, l.c., p. 58), the 
projecting tubules of the tubulated pores are much longer than in the case of P. sym- 
metricus, and thus form a stepping-stone in the series towards the condition existing 
in Eri ' ina . The pores of both kinds in Pliobothrus are devoid of styles. .The gastro- 
pore cavities are tubular in form for a short depth from the surface, and then expand 
suddenly into a wide basin-shaped chamber, which lodges the similarly formed base of 
the gastrozooid, and from the margins of which proceed numerous large canals running 
mostly to the bases of neighbouring clactylopores. The corallum is very coarsely 
porous, otherwise the finer structure is much as in Sporadopora. The ampullae are, as 
in Sporadopora , buried beneath the surface of the corallum. Pourtales remarks on 
them as “ occasional round cavities found in the centre of the branch, filled with a 
yolk-like substance contained in a membrane.” 
Structure of the Soft Parts. (Plate 41, fig. 2.) 
The coenosarcal meshwork of Pliobothrus symmetricus is very like that of Sporado- 
pora in general arrangement, as will be seen by reference to the figure (Plate 41, fig. 2). 
The tubes composing it are, however, much finer and smaller in diameter, and the 
components generally of the coral are on a smaller scale. 
There is the usual surface layer of ectoderm present, and the nematocysts which 
occur are of the two forms found in the whole of the Stylasteridse. The offsets of the 
ccenenchymal meshwork, which join the sheaths of the gastrozooids, show only a very 
indefinite trace of the radiate arrangement which is so marked in Sporadopora. A 
trace of the arrangement does, however, exist (Plate 41, fig. 2, XX). 
The gastrozooids are devoid of tentacles. In the contracted condition they consist 
of an upper cylindrical portion (Plate 41, fig. 2, Z), and a wider saucer-shaped basal 
region, to join the margins of which the lower part of the cylindrical portion gradually 
widens out interiorly. Canals are given off from the margin of the basal saucer of the 
zooid all round, and pass to join the general ccenenchymal meshwork ; but no canals 
at all are given off from the rounded under surface of the zooid. The upper surface of 
the cylindrical portion of the zooid is nearly flat, and is occupied by the mouth of the 
zooid, which is a cruciform slit bounded by elongate gastric endoderm cells, closely 
similar to those described as existing in Sporadopora. 
The dactylozooicls are simple elongate-conical bodies devoid of mouths, with a 
minute structure closely similar to that of the corresponding zooicls of Sporadopora. 
In the retracted condition they are thrown into a series of transverse folds, which are 
indicated by fine transverse lines in the figure (Plate 41, fig. 2, T Z, T Z). The zooids 
appear to be retracted directly within their sheath, and not to be attached on one side 
of their base. 
The gonophores are contained in ampulke, which are often sunk deep within the 
corallum ; and it is not apparent by what means the large mature plan u he find their 
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