REPORT ON CORALS — EXPLANATION OF PLATES. 215 



X, X. Spaces between the branches of the ccenosarcal network in the region imme- 

 diately adjoining the sac of the zooid, where these branches have a 

 peculiarly radiate arrangement, called here inter-radial spaces. 



A, A. Slips of fine membrane attached to the radial offsets. 



PLATE IV. 



Section vertical to the surface of a portion of a decalcified female stock of Err'tna 

 labiata, showing the form and dispositions of the zooids and gonophores. The meshes 

 of the ccenosarcal network are, as in Sporadopora, closer and smaller in the more super- 

 ficial than in the deeper regions of the coral. The zooids are all inclined towards the 

 tip of the branch of the coral. 

 D Z, D Z, D Z. Dactylozooids. In two of these the sac or lining membrane of the 



pore is shown as cut open, in order to exhibit its relations to the contained 



and partly retracted zooid. 



D. A dactylozooid in process of development as a bud. 



G Z. Mouth of the sac of a gastrozooid, which sac is cut open in order to show the 



contained zooid. 

 T. Tentacle of the zooid. 0. Its mouth. 

 C. Gastric Cavity. St. Style. 

 X, X. Spaces in the ccenosarcal network, homologous with the inter-radial spaces in 



Sporadopora. 

 Three gonophores are represented in the figures, showing three successive stages 

 of development, the central one of the three being most advanced. 

 V. Ovum. S. Spadix shown in section. 



In the central gonophore the planula which is shown in section is doubled up 

 somewhat, being fully developed, and ready to escape. 

 E C. Ectoderm of the planula. 



E. Endoderm. 



B. Membrane immediately covering the planula where not in contact with the spadix. 

 A. Surface layer of endoderm reflected over the wall of the ampulla. 



In the remaining gonophore the developing planula and its spadix are shown entire, 

 the surface membrane only covering the wall of the ampulla being seen in section. 

 P. Planula. 

 S'. Spadix showing the manner in which it forms a network and becomes digitate or 



fringed towards its outer margin. 

 N, N, N. Nematophores. 



