REPORT ON CORALS — EXPLANATION OF PLATES. 219 



Fig. 2. Shows the structure of the soft parts of a female stock of Pliobothrus symmet- 

 ricus. The structure is exposed by means of a section vertical to the surface 

 of the coral. The mass of the coral, the hard skeleton being removed, is 

 composed of the usual coenosarcal rueshwork which is bounded externally by 

 a continuous surface layer of ectoderm containing large nematocysts. 

 Embedded in the meshwork are two kinds of zooids and the gonophores. 

 The sac or sheath of the single gastrozooid shown in the figure is opened in 

 order to display the zooid within. 



Z. Gastrozooid. S placed in the neck of the sac of the gastrozooid. 

 X, X. Spaces in the meshwork corresponding to the inter-radial spaces 

 in Sporadopora. Here the radial arrangement is hardly to be 

 discerned. 

 D Z, D Z, Dactylozooids. The transverse lines drawn encircling the 

 bodies of these zooids indicate folds into which the bodies of the 

 zooids are thrown in extreme retraction. 

 0. Rests on a cup-shaped spadix, bearing a mature unimpregnated ovum, 



containing a germinal vesicle. 

 G. Impregnated ovum in an early stage of development. 

 P. Planula nearly mature eontained within its sac. 

 Fig. 3. Male gonophore of Pliobothrus symmetricus. 



PLATE IX. 



Shows the structure of the soft parts of Cryptohelia pudica displayed by decalci- 

 fication. 



The figure represents two cyclo-systems of zooids, together with the short branch 

 of the coral connecting them. The cyclo-system on the left hand in the figure is 

 represented as laid open by a vertical cut passing through the axis of the gastrozooid, 

 and the disposition of the several parts is here shown in detail. The breeding sac 

 of this system is in an early stage of development. The dactylozooids are shown as 

 protruded. 



In the cyclo-system on the right hand the superficial membrane is mostly left entire, 

 and the cyclo-system is not opened, but a view is obtained into the open mouth of the 

 gastropore showing the dactylozooids doubled down into it. The breeding sac is here 

 shown in its fullest activity, and containing a planula ready for emergence. The sac is 

 represented as cut open in order to exhibit the contained structures. 

 G Z. Cavity of the sac of the gastrozooid. 

 0. Mouth of the gastrozooid, which is devoid of tentacles. 



