ME, H. 1ST. MOSELEY ON THE STRUCTURE OF THE STYLASTERIDyE. 497 
dichotoma, taken at a point above the junction of the tentacles with the 
body of the zooid. Hence the tentacles appear in this section as isolated 
structures. 
S. Digestive cavity. 
G. Large gastric cells with their nuclei. 
M. Muscular layer and basement membrane at this region of the zooid 
comparatively little developed. Shows longitudinal fibres cut 
across. 
E. Ectoderm here containing very few nematocysts but numerous 
nuclei. 
T, T. Tentacles in section. 
Fig. 2. Section transverse to the longitudinal axis of a large dactylozooicl of Spora- 
dopora dichotoma. 
B. Body cavity of the zooid. 
L. Endoderm consisting of a double layer of large transparent nucleated 
cells with smaller cells on its inner aspect. 
M. Muscular layer and basement membrane showing a series of stout 
isolated fibres. 
E. Ectoderm. This forms a thick layer which contains numerous nuclei 
and developing nematocysts, and at its outer surface is protected 
by a continuous layer, one cell deep, of nematocysts of the 
smaller form. 
Fig. 3. Section parallel to the surface of the soft tissues of Sporadopora dichotoma ; 
taken at a very slight depth just beneath the superficial layer of the 
ectoderm. The soft structures about the mouths of the sacs of a 
gastrozooid and a contiguous dactylozooid are shown, and the radiate 
arrangement of the coenosarcal tubes around the sac openings. 
G Z. Lumen of the upper part of the sac of a gastrozooid. 
R M. Wall of the sac containing radially disposed fusiform muscular 
elements which are prolonged outwards on to the radial offsets of 
the coenosarc. The wall of the sac is lined internally by small 
rounded cells. 
R, R. Radially disposed offsets of the coenosarcal meshwork which pass 
inwards to join the outer surface of the sac all round. 
A, A. Slips of fine transparent membrane containing nuclei attached to 
the radial offsets. 
X, X. Inter-radial spaces. 
D Z. Lumen of the sac of a dactylozooid with somewhat similar 
arrangement to that in the case of the gastrozooid. 
N. N. Nematophores. Closely packed batteries of the larger form of 
nematocysts, which are here seen in transverse section. 
3 s 2 
