REPORT ON CORALS — EXPLANATION OF PLATES. 217 



Z. Gastrozooid with twelve tentacles, disposed in a single whorl, and an almost hemi- 

 spherical hypostome. Large canals spring from the base of the zooid, and 

 form communications with the basal canals of adjacent zooid cyclo-systems. 



D Z', D Z'. Dactylozooids in tbeir sheaths seen from behind within the adjacent 

 zooid cyclo-systems. 



G, G, G. Gonophores. The sac of one of these is cut open to show the ovoid male 

 generative masses and their spadices lying within. 



PLATE VII. 



Shows the structure of Stylaster densicauUs as seen in the decalcified condition. 

 The cylindrical masses formed by three cyclo-systems of zooids are shown cut open, so 

 as to demonstrate the arrangements of the zooids and coenosarcal ramifications within 

 them. The positions of the two additional cylco-systems are indicated by outline. 

 In the centrally placed cyclo-system the entire ramifications of the coenosarcal canals 

 are shown. 



In the system displayed on the left side of the figure, the wall of the sac of the 

 gastrozooid, and the superficial network beneath it, are removed, in order to show 

 the connections of the bases of the dactylozooids with the deeper canals. 



In the system shown on the right in the figure, the details of the connection of the 

 base of the gastrozooid with the coenosarcal canals only are given. 



The gonophores are seen through the superficial networks existing in the walls 

 of the ampulla. 



Z, Z. Gastrozooids situate one at the base of each cyclo-system. 

 D Z, D Z. Dactylozooids. G G. Male gonophores. 

 N, N. Nematophores. 



A. Reflection of the surface layer of the ectoderm forming the sac of the gastrozooid and 



lining the gastropore. The sac-wall is very thin and transparent. Curved 

 lines crossing the dactylozooids transversely about their middles, in the 

 central cyclo-system shown in the figure, mark the lower and innermost 

 margins of the dactylozooid sacs, where these become continuous with the 

 sac of the gastrozooid. In the cyclo-system shown on the left in the 

 figure, the sac of the gastrozooid and the portions of the sacs of the 

 dactylozooids fronting the gastropore are represented as removed, together 

 with the superficial network of the ccenosarc immediately beneath them, 

 in order to display the connections of the deeper systems of large main canals 

 which connects the zooids of the cyclo-system directly with one another. 



B, B. Spaces in this deeper system of main canals. 



(ZOOL. CHALL. EXP. — PART VII. 1880.) G 28 



