MR. H. N. MOSELEY ON THE STRUCTURE OF THE STYLASTERIDHD. 
433 
As will be seen by reference to Plate 36, the coenosarcal canals form in Sporadopora 
a very complex network, which brings, by means of the freest anastomoses in all 
directions, the several members of the compound organism into complete circulatory 
connexion with one another. 
The interspaces in the meshwork occupied in the recent condition of the coral by 
hard masses of the corallum, are larger and wider in the deeper regions of the coenosarc 
than nearer to the external surface. For here the meshwork is much closer, and the 
mass of soft living tissue much greater in proportion to the calcareous structures 
secreted by it, than is the case in the deeper regions. Further, the deeper canals are 
ol greater calibre than those nearer the surface. Towards the deepest regions of the 
coenosarc the canals are shrunken and atrophied, and pass off into effete and almost 
dead fragments of tissue, which form the inner boundary of the living lamina. 
The largest trunks of the meshwork are those which proceed directly from the bases 
of the zooids and gonophores. These are soon reduced in size by branching, and are 
lost in the general anastomosis. 
Around the sacs containing the zooids the canals of the coenosarc have a special 
radiate disposition (Plate 43, fig. 3). The radial canals occupy an area circular in 
outline, extending all around the outer sides of the sacs of the zooids. They pass 
directly inwards radially, from the margins of the areas where they take origin from 
the general meshwork to join themselves on to the walls of the zooid sacs, towards the 
centres of the areas. They branch but seldom on their course, and then only towards 
their outer origins, where they not uncommonly bifurcate. 
As may be seen from the figure, the radial canals, which lie at successive depths 
from the surface, do not correspond in any way in position with those above or below 
them, but are quite irregular as far as radial disposition is concerned. In vertical 
sections, however, of the living lamina (Plate 36), these radial canals are seen to succeed 
one another at tolerably regular intervals, in vertical disposition, with a somewhat 
regular series of interspaces between them. 
This radial disposition of the canals is less marked around the sacs of the larger 
dactylozooids than around those of the gastrozooids, and is hardly apparent around 
those of the smaller dactylozooids. Traces of it are to be seen around the sacs of the 
gonophores, as at G', Plate 36. Although towards the periphery of the area occupied 
by them these radial canals contain endoderm cells, and appear similar in structure to 
the other canals of the coenosarc, towards their inner extremities, where they join the 
zooid sacs, they become diminished in size, and often appear as mere slips of trans- 
parent tissue, having a fibrillate appearance. 
Muscular filaments, continued from ovoid muscular cells embedded in the walls of 
the zooid sacs, pass outward along the radial offsets, and are attached to them in the 
region about the mouths of the sacs (Plate 43, fig. 3, PM). 
Attached to the radial offsets, and often extending over the interspaces between 
adjacent ones, slips of a fine transparent membrane, containing minute nuclei ancl 
3 K 2 
