platp: II. 



MADREPORA MURICATA IJnna-us. 



Fig. 7. — Transverse section through a portion of the external covering of tlie skeleton (coenosarc) and the superticiai 

 longitudinal canals. The outer endoderm of the canals is crowded with zooxanthellie, while they are 

 more sparse internally, wliere the endoderm is narrow. The calicoblast layer has almost disappeared, 

 liut the denser part of the skeletal matrix remains, associated with desmoidal processes. X 320. 

 Fi(i. .s. — Transverse section through the tissues covering the uppermost part of the skeleton of an apical ]iolyp, 

 representing a superticiai canal and part of one adjacent on the right side. The outer ectoderm i.s 

 much broader than in the previous figure, and the calicoblast layer {cnl.) is also better developed. The 

 endoderm lining the canals is devoid of zooxanthella', and the uiesogla'a is only a mere lamella. 

 X 320. 

 -Cells from the cccnosarc: u, Two varieties of nematoblasts; /<, supporting cells; r, granular cell from 



endoderm, containing two zooxanthelloe. X 450. 

 -Transverse section through a portion of a tentacle .showing the well-developed nerve layer (»»•. /. ), the 



cnidocils, and cilia on the ectoderm and endoderm. X 320. 

 -Longitudinal section through the disk ami uppermost part of the stomod;eal wall. X 320. 

 -Transverse section through two mesenteries (directives), and the stomodieal wall and skeletotrophic 



tissues to which they are attached. X 300. 

 -(I, Two gland cells from the stomod;eum; h, group of ciliated supiiorting cell.s from thestomodicum. ■ 450. 

 -Transverse section through a mesentery, terminateil by a mesenterial filament. X 320. 

 -Cells from mesenterial filament; a, various gland cells; h, nematoblast; c, supporting cells fmni posterior 

 region of filament; d, cell with zooxanthelL'e from the mesenterial epithelium. X 450. 

 Fuj. 16. — Transverse section through a canal near the apex of a branch, showing the deep calicoblast layer, an<l the 



narrow ciliated endodermal lining of the canal. X 320. 

 Fio. 17. — Section through a decalcified canal wall some distance from the apex. X 320. 



Fici. IS. — Section through the wall of a canal, and a portion of the organic matrix remaining after slow decalcification. 

 The section is taken from near the growing apex of a lirancli. Toward the upper part the matrix is still 

 connected with the canal wall, but elsewhere has become slirunken from it. The matrix shows no 

 cellular structure, but in a])pearance \-er\- closely resembles the actual skeleton as seen in surface view 

 {cf. fig. 19). X 320. 

 Fig. 19. — Surface view of part of the macerated corallum near the growing apex. X 320. 



Fig. 20. — Mesentery from a liud, showing the early development of the mesenterial filament; the latter is at first 

 indistinguishable from the mesenterial epithelium. X 320. 

 602 



