212 THE VOYAGE OF H.M.S. CHALLENGER. 
the border behind this wall all round a narrowed prolongation of the 
lower chamber of the gastropore passes up, and leads above by a series 
of offsets to the lower terminations of the tubular portions of the dactylo- 
pores, conveying, in the recent condition of the coral, the main canals 
springing from the gastropore. The support of the lid of the pore system 
sends a stout prolongation downwards to fuse with the wall of the upper 
chamber of the gastropore. 
GP. Upper chamber of the gastropore. 
GP’. Lower chamber of the gastropore. 
DP, DP. Dactylopores. 
C. Space behind the wall of the upper gastropore chamber leading to the 
dactylopore tubules. 
L. Lid covering the cyclo-system. 
Fig. 8. Pore system of Astylus subviridis laid open by a vertical incision through the 
axis and in the direction of the length of the supporting branch. 
GP. Upper chamber of the gastropore. 
GP’. Lower chamber of the gastropore. 
B. Tongue-like process of the lower border of the wall of the upper 
chamber of the gastropore, which projecting horizontally in the 
direction, in each system, of the tips of the branches, converts the 
aperture leading between the two chambers into the form of a 
horseshoe, 
A. Base of the tongue-like process and part of the wall of the upper 
chamber cut through. 
CC. Space behind the wall of the upper gastropore chamber, leading, as 
in the last figure, to the dactylopores. 
G, G. Ampulle. 
Figs. 9-16. Diagrammatic representations of the arrangements of the gastropores and 
dactylopores in the several genera of Stylasteridee, to show the manner 
in which cyclo-systems and their pseudosepta have become developed in this 
family. 
The following letters apply similarly throughout the series :— 
G Z. Gastropore. 
S. Its style. 
D Z. Dactylopore. 
Vig. 9. Sporadopora dichotoma. The pores of both kinds are irregularly scattered over 
the surfaces of the ccenosteum. 
Fig. 10. Allopora nobilis. A number of dactylopores are grouped in a circle around a 
single centrally placed gastropore. 
