18 G. HERBERT FOWLER. 



EXPLANATION OF PLATES I and II. 



Illustrating Mr. G. Herbert Fowler's Paper on "The Anatomy 

 of the Madreporaria/' III. 



Fig. ] . — Transverse section through a small part of the crateriform colony 

 of Turbinaria sp. (vide p. 2). Ab. Abaxial, inner, or ventral surface of 

 the colony. Ax. Axial, outer, or dorsal surface of the colony, a. Oblique 

 section through a polyp cavity, b. Transverse section of a polyp cavity near 

 its orifice, c — c. Similar sections further from the orifices. (Camera lucida.) 

 Fig. 2. — Diagrammatic transverse section of a polyp of Turbinaria sp. 

 (p. 3). In this and similar diagrams the ectoderm is represented by 

 " blocked" black and white, the mesoglcea by a dark line, and the endoderm 

 by a light line, the calcareous skeleton being dotted. The thicker and con- 

 torted ectoderm at the upper part of the stomatodseum represents the taller 

 cells, interspersed with plentiful nematocysts, occurring in the neighbourhood 

 of the tentacles, i. e. mouth disc rather than stomatodseum. Twenty-two pairs 

 of mesenteries occur in this polyp, of which eleven are on the right and nine 

 on the left of the " directives." A bit of the external body wall is drawn to 

 show its relations to the echinulations. Ab.D. Abaxial directives. Ax.D. 

 Axial directives. St. Stomatodseum. Ed. Ectoderm. Me. Mesoglcea. En. 

 Endoderm. (Cam. luc.) 



Fig. 3. — Transverse section of a mesentery of Turbinaria sp., bearing an 

 ovum with nucleus, nucleolus, and nucleoleoli. The lengthening of the endo- 

 derm cells round the ovum is noticeable. 



Fig. 4. — Transverse section of the calyx of Lophohelia prolifera near 

 the lip (vide p. 7). The darker parts represent " centres of calcification," 

 or the earliest deposited portions, which become enlarged into the regions 

 marked respectively T. (thecal), or S. (septal), according to their origin. The 

 regions are bounded by " sutures." Ect. s. Ectocoelic septa. Ent. s. Ento- 

 ccelic septum. 



Fig. 5. — Similar section of Lophohelia prolifera at some distance 

 from the lip of the corallum. The " centres of calcification" of the ectocoelic 

 septa and of the theca have run into one line, owing to the growth of the 

 latter upwards to the former. Lettering as in Fig. 4. 



Fig. 6. — Diagrammatic transverse section through a segment of Lopho- 

 helia prolifera. The septa are seen to stand in both ectoccelic and ento- 

 ccelic spaces. The peripheral sections of these spaces and the peripheral 

 lamellse of the mesenteries, cut off by the upgrowth of the theca, are also 

 apparent. Lettering as in Fig. 2. 



