494 SUMMARY OF CURllENT RESEARCHES RELATING TO 



deeper parts of the ccenenchyma, and larger, spinj and spindle-shaped, 

 usually white, spicules are in its outer part. No spicules were found in 

 the polyps. 



The ectoderm has the usual cover-cells, nematocysts, sense-cells, 

 interstitial, ganglion, and muscle-cells. Small nematocysts are found in 

 the ectoderm of the column, tentacles, and stomodteum of the polyps. 

 Large ones in considerable numbers are grouped into batteries in the 

 coenosarc. Ganglion cells are very few, and muscle-cells are found on 

 the oral side of the tentacles and disk only. In the ectoderm of the 

 coenosarc between the polyps some of the cells have each a prominent 

 supporting fibre, which runs from near the nucleus perpendicularly to 

 the mesogloea. 



The mesogloea is thin, except in the coenosarc regions, where it is 

 very thick. Cords of cells like the interstitial cells of the ectoderm 

 can be traced from the ectoderm to the deeper layers of the mesogloea. 

 In these cords there are partly formed and fully formed nematocysts, 

 spicule-cells, and cells of irregular shape, sometimes containing granules. 

 These irregularly shaped cells form a transition to the jelly-secreting 

 cells, which are small and have many long branches. Large spicules are 

 produced by characteristic secreting cells with large granules and one 

 or many nuclei. Spheroidal nutrition cells occur in many colonies, in 

 both ectoderm and endoderm. They probably originate in the endoderm 

 of the canals which form a network through the mesogloea. 



The endoderm cells are of characteristic form, being united to each 

 other at the proximal and distal ends, but, in fixed material, separate 

 elsewhere. In the tentacles, in the polyp-wall, and in many canals, they 

 contain numerous zooxanthellae. Except in the tentacles and the longi- 

 tudinal canals, they have myonemes running circularly. Unicellular 

 mucus-glands and granular cells, that are probably digestive in func- 

 tion, are numerous. The cells of the longitudinal canals differ from 

 other endodermal cells in being much longer and in having no trace of 

 myonemes. 



Digestion is accomplished by cells of the stomod8eum, by the six 

 ventral and lateral mesenteric filaments, and by scattered gland-cells in 

 the walls of the body-cavity and the canals. The stomodfeum has, 

 besides the supporting cells, mucus- and granular gland-cells. The 

 mesenteric filaments, except the dorsal pair, are very short, and their 

 epithelium is composed of granular gland-cells only, which give some 

 evidence of intracellular digestion. Slow-moving organisms, which 

 serve as food, are often transferred from the surface of the coenosarc 

 between the polyps, where large stinging cells abound, to the mouth 

 of a polyp, that independently contracts to the level of the coenosarc 

 with its mouth open. The two dorsal mesenteric filaments are very 

 long and sinuous, with very characteristic cells. The sides of the groove 

 are lined by cells with strong cilia, but the central cells show the 

 character of mucus-cells and produce a mucous secretion. 



The muscular system is like that of AUyonlum. The colony is weak 

 in its responses and has few nerve-elements. The response to touch is 

 not quick, and the coenosarc between the polyps is more sensitive than 

 the polyps themselves. 



