216 THE VOYAGE OF H.M.S. CHALLENGER. 



PLATE V. 



Longitudinal section through the axis of a branch of a stock of Spinvpora echinata, 

 decalcified, showing the ccenosarcal network and the surface membrane, with the 

 various zooids in their mutual relations. 



D Z, D Z, D Z. Indicate some of the larger dactylozooids, of which many are shown. 

 These larger dactylozooids are situate near the extremities of spine-like 

 processes of the ccenosteum, represented here by the corresponding laminae 

 of soft tissue, extensions of the surface layer of ectoderm. The processes 

 are grooved on the side lying towards the tips of the coral branches, for 

 the reception of the zooids, which are all shown here as much contracted. 



A, A. Examples of the fusing of two adjacent processes. 



B, B. Processes represented as cut open in order to show the disposition of the bases 



of the dactylozooids within, and their connection with the ccenosarcal 



network. 

 D, D. Small dactylozooids protruded from simple pores near the bases of the spine-like 



processes. 

 G Z, G Z, G Z. Gastrozooids seen ; some retracted within their sacs, others partially 



expanded. They have each a well-developed hypostome and six tentacles, 



and join the ccenosarcal network at their lower extremities by means of 



four main canals. 



PLATE VI. 



Vertical section through one of the cyclo-systems of zooids of a male stock of 

 Allopora profunda decalcified. Right and left of the centrally placed system, seen in 

 section, are represented parts of two other similar systems, which are shown as seen 

 from their outer aspects by transmitted light, and not in section. 



D Z, D Z. Dactylozooids retracted. Arranged in a circlet around the mouth of the 



pore of the gastrozooid. 

 P, P. Sacs, or soft tissue walls of the pores, of dactylozooids. separated from one 



another by pseudosepta. Two of these sacs are shown cut open to display 



the attachment of the bases of the zooids within them. 

 G Z. Sac of the gastrozooid, between which and the place occupied in the recent 



condition by the wall of the pore of the zooid is a wide space, traversed 



by radially disposed offsets of the ccenosarcal network, R R. 

 X, X. Inter-radial spaces between these effects. 



