220 THE VOYAGE OF H.M.S. CHALLENGER. 
S. Digestive cavity of the zooid lined with elongate gastric cells. 
M. Longitudinal muscular layer of the zooid. As in Astylus subviridis, numerous 
canals pass off from the margin of the rounded base of the zooid, but none 
from the under surface of base itself. 
D Z, DZ. Dactylozooids. 
P. P. Mouths of the sacs of the dactylozooids. 
L, L. Peculiar protective laminz, or lids, folded in this genus in front of the openings 
of the cyclo-systems. In the case of the left-hand system of the figure the 
ramifications of the superficial network of the ccenosarc, prolonged into the 
body of the lid, are shown, and also the nematophores with which the lid 
is provided. In the other system represented, the superficial layer of the 
coenosare is shown intact. The downward prolongation of the base of the lid 
which should pass between the sac of the gastrozooid and its main 
upward canals, is omitted for clearness’ sake. 
N, N. Nematophores. One of these is situate at the outer margin of the cyclo-system 
in each interval between the sacs of the dactylozooids. 
G. Female gonophore contained, with two others im earlier stages, in a special brood-sac 
as yet not far advanced in development. 
}. Brood-sac in full development containing ova and embryos in all stages of develop- 
ment. 
Oy, Ov’. Fertilised ova in advancing stages of development and cell multiplication. 
P 1. Early stages of planula embryo. The thin ectoderm appears as just differentiated. 
P 2. Planula fully advanced with more fully developed and thickened ectoderm. 
P 3. Fully developed planula with highly differentiated ectoderm containing nemato- 
cysts, &e. 
PLATE X. 
Shows certain details of structure of the soft parts of Sporadopora dichotoma and of 
Astylus subviridis. 
Fig. 1. Section transverse to the longitudinal axis of a gastrozooid of Sporadopora 
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. 
