XI 



Explanation of the Plates. 



pl i. 



Figure i. Duva rosea, natural size. 



— 2. A branch of the same animal with its divers ramifications, highly magnified: a) division of the main branch; 



b) 4 or 5 branchlets; c) 4 or 5 stalks, bearing each from 5 to 7 polyps. 



— 3. A polyp, magnified. 



4. A longitudinal section of 2 polyps, united at the base, magnified: a) the elliptic oral orifice; b) the oesophagus. 



5. A longitudinal section of the anterior part of the polyp-body, together with half of the oesophagus, highly 

 magnified: a) outer epithelium (ectoderm) underneath which is a strip of connective tissue, whence proceeds 

 a septum; b) longitudinal muscular fibres on the septum, attached to the oesophagus; c) transversal muscular fibres, 

 also attached to the oesophagus; d) epithelial cells in the upper part of the oesophagus; e) epithelial cells (ento- 

 derm) in the lower part of the oesophagus. 



— 6. Transverse section of a branchlet, magnified : a) prolongation of connective tissue (septum) ; b, b) the two septula, 



bearing each two long gastral filaments; c) connective tissue with alimentary canals. 



— 7. Transverse section of a trunk, showing the septa and principal canals, natural size. 



— 8. Transverse section of a small part of a branchlet, highly magnified: a) a long gastral filament, borne byaseptulum; 



b) transversal muscular fibres on one side of the septulum; c) longitudinal muscular fibres on the other side; d) the 

 inner epithel (ectoderm); e) delicate alimentary canals in the connective tissue; f) constricted gastric cavity of a 

 polyp, filled with epithel, and corresponding to a delicate alimentary canal. 



— 9. Nutritive canals in the connective tissue of the septa, magnified. 



— 10. Transverse section of the medial part of a polyp, magnified: a) the outer epithel (ectoderm); b) connective tissue; 



c) a septum between the wall of the body and the oesophagus; d) the inner epithel (entoderm), investing the 

 divers chambers. 



PL IL 



Figure 1. The outer epithel (ectoderm) of the zoanthodeme of Duva rosea, magnified 650 times, drawn by Camera lucida. 



— 2. The inner epithel (entoderm); equally magnified. 



3. A piece of sidn from the lower part of the trunk of Duva rosea, in which are seen the closely-set spicules, 

 magnified. 

 Figs. 4, 5, 6, 7, 8. The same spicules, highly magnified. 

 Figure 9. A piece of skin farther up the trunk of Duva rosea, in which the spicules occur widely separated, magnified. 



— 10. A spicule from the coenenchym on the lower part of the trunk in Duva rosea, highly magnified. 



— 11. Corpuscles of connective tissue in Duva rosea, magnified 850 times, drawn by Camera lucida: a) offshoots con- 



taining protoplasma. 



— 12. a, b, c, d) spicules from the anterior half of the body of a polyp on Duva rosea, highly magnified. 



— 13. Transverse section of a group of polyps on Duva florida, with generative products, magnified. 



— 14. A piece of the trunk of Duva florida. together with a main branch and its ramifications, slightly magnified: 



a) grooves on the trunk; b) a main branch; c) branchlets, with their ramifications, at the extremities of which the 

 polyps occur. 



— 15. A polyp from Duva florida, magnified: a) suture with the adjoining polyp; b) the series of spicules on the aborai 



surface of the tentacles, 



— 16. A piece of skin from the lower part of the trunk in Duva florida, showing the spicules placed one upon the other, 



magnified. 



— 17. a, b, c) the same spicules, highly magnified. 



