ON A NEW SPECIES OF CORYMORPHA FROM JA TAN. 



157 



and arc arranged in a more or less regular row, while those in the 

 mass arc polygonal owing to mutual pressure (fig. 4). further, the 

 cells near the free surface are roundish and loosely aggregated ; and 

 those most internally situated are quite free, presenting a rpherical 

 shape. Free cells of strikingly similar nature to those just mentioned 

 are found not only in the vicinity of the glandular epithelium, but 

 also in a large number in every part of the hydranth-cavity, in 

 gonosomal-cavities as well as in longitudinal canals of the hydrocaulus. 

 All these free cells are readily distinguishable from ordinary tissue- 

 cells by their small size and their remarkably small nucleus. Never- 

 theless, the nucleus is structurally quite the same as that of tissue- 

 forming cells, i. c, it has a distinct nuclear membrane, peripheral 

 chromatin granules, and a central nucleolus. Thus there is little 

 doubt that the wandering cells referred to arc derived, so to say, 

 budded off, from the zone of the modified epithelium in question, 

 Most wandering cells, especially those in the hyposomal cavity, are 

 found to differ slightly from the cells composing, or in the vicinity 

 of, the formative epithelium, in being of a larger size and in showing 

 a feebler staining capacity. Judging from the results of differential 

 staining, it is plain that the swelling of the wandering cells is ap- 

 parently due to imbibition of fluid, which accumulates in the narrow 

 space between the pellicle and the periplasma. The cytoplasm of 

 such wandering cells is also characterized by containing a few minute 

 granules of a brown color. Various sorts of such cells, which I take 

 to represent degenerating stages, are abundantly met with in the hy- 

 postomal cavity mingled with food detritus. Although I take it for 

 certain that the modified epithelium of the hypostomal endoderm gives 

 rise to those wandering cells, yet it is altogether uncertain whether or 

 not the cells arise by mitosis from the epithelial cells, since division 

 figures have not been met with in any part of the structure in both 

 adult and young individuals. 



Hydrocaulus. The hydrocaulus becomes gradually narrower to- 



