EXPLANATION OF PLATE IIL 



MURICEA— SP. 



Fig. I . Small zoanthodeme sho-a>ing pinnate maimer of branchings and expanded 

 polyps. 



Fig. 2. Living and expanded polyp, magnified : a, surface of branch with 

 spicules showing through the ectoderm; b, expanded tentacle of polyp; 

 c, mesentery showing as a ridge. 



Fig. 3. Oral viezv of living and expanded polvp ■' a, a, tentacles; b, b, mesen- 

 teries; c, mouth. 



Fig. 4. Transverse section of branch near tip, mag nijied: a, axis cylinder ; b, 

 endodermal investment of axis; c, mesodermal coenenchyma surround- 

 ing b; d, d, endodermal lining of primary water- vascular canals; e, 

 epithelium covering zoanthodeme; f, f, f, retracted polyps; g, g, pri- 

 mary canals; h, h, mesenteries; i, ovum. 



Fig. 5. Longitudinal section of axis and one side of branch: a, axis cylinder 

 showing superimposed lamelhe; b, endodermal investment of axis; 

 c, coenenchvma containing spicules; d, d, d, endothelial lining of 

 water-vascular canals — on the right, this is shown to be continuous 

 with lining of calicles; e, fibrous sheath of axis; f, f, longitudinal sec- 

 tion of primary canal, showing its connection with calicle; g, retracted 

 polyp; h, epithelium; i, i, retractor muscles; j, ovum; k, k, k, granu- 

 lar rows of cells in ccenenchvnia; 1, 1, 1, spicules. 



Fit;. 6. Transverse section of polyp {diagrammatic) to illustrate relation of 

 ectoderm, endoderm, and mesoderm : a, a, a, mesoderm comprising cen- 

 tral plates of mesenteries, middle layer of body wall, and the portion of 

 gullet between the external and internal surfaces; b, b, b, endodermal 

 lining of all the inter-mesenterial chambers; c, c, c, muscle layer 

 comprising retractor muscles and situated on the ventral surface of 

 the mesodermal plate of each mesentery ; d, ectodermal lining of gul- 

 let formed by inversion from oral surface. 



Fig. 7. Longitudinal section of tip of branch, to illustrate formation of end of axis 

 cylinder: a, axis cylinder; b, b, its endodermal investment continuous 

 with lining of terminal polyp; c, c, coenenchyma; d, d, d, small canals; 

 e, epithelium; f, f, spicules; g, g. granular rows of cells. 



Fig. 8. Portion of a cross section of a branch near tip, to show relation of parts 

 to axis: a, periphery of axis; b, columnar cells of investment of axis; 

 c, coenenchyma between investment and d; d, quadrate endodermal 

 cells forming lining of primary canal. 



I'^lG.s. 10, II, 14, 19. Regular tuberculate spicules. 



F'uis. 12, 13, 15, 16, 17. Unsymnietrical cchinate spicules. 



Fk;. 18. ^uadri-partite spicule. 



