MR. H. N. MOSELEY OIL THE STRUCTURE OF THE STYLASTERIDYE. 
439 
in other Hydroids, and there can he little doubt that they are gastric in function. It 
will he observed that they do not occur in the endoderm of the mouthless dactylozooids. 
Towards the base of the zooicl cavity these cells become shorter and shorter in length, 
until in the deepest regions they become mere small globular transparent cells, like those 
composing the endoderm of the dactylozooids. Towards the base of the zooid they 
are farther overlaid by a layer of the pigmented endoderm cells, which form the 
endodermal lining of the general ccenosarcal mesliwork. The lining of the coenosarcal 
canals thus becomes continuous with that of the zooid cavity (Plate 36). 
The calcareous style projecting up into the cavity of the zooid has reflected over it 
from its base a covering of ectoderm, and over that it is protected within the zooid 
cavity by a layer of ordinary pigmented endodermal cells (Plate 36, St). 
The tentacles of the alimentary zooid of Sporadopora dichotoma were the only ones 
amongst those of all the Stylasteridse which I was able to observe in the fresh condition, 
and time did not allow of more than a cursory glance at these even. It sufficed, 
however, to show that the tentacles are, as in the case of Millepora, knobbed at their 
tips (Plate 43, fig. 4), and that their stems display the usual characteristic transverse 
segmentation of the endoderm. 
The knobs of the tentacles are ovoid in form and are densely beset with nematocysts 
of the smaller variety. The ectodermal layer of the stems of the tentacles contains 
few or no nematocysts. 
Gonophores . — Although the soft parts of at least three different colonies of 
Sporadopora dichotoma were examined, these specimens proved all to be male. In all 
the specimens gonophores were very abundantly present. They occupy the ampullar 
chambers in the calcareous corallum already described (Plate 35 , fig. 1, G). The male 
gonophores are ovoid bodies with their long axes directed at right angles to the 
surface of the coral. Sometimes only one such body is present in an ampulla, 
sometimes two or three. The outer extremities of the gonophores are sometimes 
drawn out into a short tail-like prolongation (Plate 36, G). The bodies vary 
considerably in dimensions. Often a gonophore which is fully mature and just ready 
to discharge its contents at the summit of its ampulla (as seen in Plate 36, G), has 
beneath it in the deeper part of the same ampulla an immature gonophore, around 
which latter the ampulla is less dilated. 
The gonophores are composed of a spadix, which is extremely conspicuous in the 
fresh condition of the tissues, because it is full of red endodermal cells, and thus deeply 
pigmented, and a mass of testis cells or spermatozoa. The spadix is cylindrical in 
form, with a rounded extremity. It occupies the axis of the deeper region of each 
gonophore. It thus forms the core of the spheroidal body, the remainder of the mass 
of which is composed of spermatozoa or the cells from which they are developed in 
various stages of advancement. These cells and spermatozoa are contained within a 
fine and transparent but tough membrane, which invests the whole body of the testis, 
being derived from the ectoderm. I believe that a layer of the ectoderm invests the 
MDCCCLXXVIII, 3 L 
