CASSIOPEA XAMACIIANA. 203 



The vesicular bodies give rise to the white markings that were mentioned in the 

 description of the species. These vesicles are much larger than the colloblasts. Each 

 one seems to be made up of a wall of exceedingly minute refractile granules, surrounding 

 a clear space. That this body is a cell, however, is shown by the presence of a nucleus 

 pressed closely against one side. 



The green cells, or zoanthelae, are widely distributed throughout the mesogloea, but 

 are most abundant in the umbrella. They are not infrequently found imbedded in the 

 endodermal epithelium. The living cells have a greenish brown color, which they 

 impart to the animal as a whole. They are of considerable size, are globular, 

 without projections of any kind, and are generally to be found in clusters of two or more 

 (za, Figs. 52, 56, and 63) . Each one contains a nucleus and numerous granular bodies, 

 and apparently is surrounded by a cell wall ; but the latter is hard to distinguish from 

 the edge of the adjacent matrix. 



Keller thought that similar bodies in C. polypoides could not be algae, because he 

 failed to find any evidence of a cellulose cell wall. He regarded them, therefore, as 

 essential elements of the " mesoderm." 



In those of my specimens, however, which have been killed in Erlicki's fluid and 

 stained with borax carmine, the nucleus of these cells is found to be red, while the gran- 

 ular contents of the cell are bright green, and there are often one or two green bodies 

 present that are as large or larger than the nucleus. They have all the appearance of 

 chlorophyl bodies, and it is well known that the chlorophyl of some algae is not readily 

 removed by alcohol. Moreover, in teased preparations treated with iodine solution these 

 cells are found to be filled with granules that quickly turn deep blue, evidently starch. 

 The test for cellulose with iodine followed by sulphuric acid, gave, however, unsatisfac- 

 tory results. The outline of the cell would become distinctly darker, but not recognizably 

 blue. In the same way with chloriodide of zinc, a very marked reaction for starch was 

 obtained, the granules becoming almost black ; but so long as the object was viewed 

 by direct transmitted light, no reaction for cellulose could be detected with certainty. 

 On the other hand, when the light was thrown upon the object obliquely by means of a 

 condenser with a central diaphragm, the effect was quite different. The starch granules 

 became a deep ultramarine, and the parts of the cell not occupied by the starch appeared 

 distinctly violet, showing without doubt the presence of cellulose. 



Both starch and cellulose, as well as some form of chlorophyl, having been demon- 

 strated in them, there can be no further question that the green cells in Cassiopea are 

 symbiotic algae. 



The Oral Arms and their Branches. The eight oral arms (Fig. 34) arise from 

 the central oral disc at about equal intervals; and when an arm is extended, the distance 



