754 PROCEEDINGS OF THE AMERICAN ACADEMY. 



of the cell and takes on a charactei istic shape (Figs. 25, 28). Several 

 nuclei are to be found in the cytoplasm enveloping most of the spicules, 

 thus showing that the spicule-cell usually divides more than once. 

 Figure 25 shows the arrangement of the organic matter of the spicule 

 after decalcification; this is similar to the condition described by 

 Bourne. 



Certain of the cells in the mesogloea (Plate 4, Figs. 48-51) show 

 ovoid or globular bodies similar to those described by Bourne ('99) 

 and Woodland (:05) as possibly stages in nematocyst formation. 

 Rounded nutriti^'e cells also occur, sometimes few, but in the coeno- 

 sarc of some colonies very abundantly. They are also found occasion- 

 ally scattered among the ectoderm cells of the outer edge and also 

 among endoderm cells, where they probably originate. They stain 

 more deeply with eosin than the surrounding cells. 



Endoderm. 



The endoderm lines the coelenteric side of the stomodaeum, the 

 disk, the polyp wall, the mesenteries and all the canals. It is composed 

 of three types of cells; supporting, mucus, and granular gland cells. 

 Muscle cells are found in some parts. The cell characters are similar 

 in the endodermal lining of the anthocodia (Plate 2, Fig. 20), the 

 polyp chamber (Plate 4, Fig. 56) and the connecting canals (not 

 including the long nutriti\'e canals) . The supporting cells are narrow 

 and columnar, in contact with each other proximally and distally. 

 In partially contracted individuals (Fig. 20) the supporting cells and 

 the less numerous gland and mucus cells appear crowded into close 

 contact; but in slightly expanded individuals (Figs. 55, 56) after 

 fixation frequent spaces occur separating individual cells except at 

 their two ends. The cytoplasm is coarsely vacuolated. A large 

 nucleus is found somewhere in the basal two thirds of the cell. The 

 cells are sometimes crowded with Zooxanthellae (zo.v), which are 

 usually very numerous in and near the polyps, but are not so abundant 

 in the deeper canals. Three, four, or more of these algae are common 

 in the sections of each cell in the tentacles, polyp wall or outer 

 coenosarc. Each endoderm cell has a single weak cilium inplanted 

 in its free end, and at its attached end a raj'oneme, which runs 

 circularly in the wall of the anthocodia and polyp chamber, and 

 generally so in the canals. Mucus glands are abundant (cl. m iic.) ; 

 they appear as columnar cells with the cytoplasm in the form of a 



