66 JOHNS HOPKINS UNIVEESITY MORPHOLOGICAL MONOGRAPHS. 



cells. Yet, that they pass to the supporting lamella, just as Conant 

 shows in Fig. 13, would seem to indicate that they are fibers from 

 the supporting lamella or processes of the epithelial cells. While this 

 stands as an objection to their being sensory fibers, yet I cannot 

 explain away their being continued distally as a flagellum, except I 

 assume this continuation to be an artefact. This does not seem 

 probable. Perhaps they serve both purposes ; namely, that the cell 

 body with its axial fiber is continued to the supporting lamella, the 

 cell proper ending there, while the axial fiber is continued as a nerve 

 fiber. I believe this to be the proper explanation. 



The epithelium of the peduncle is quite like the epithelium of the 

 club just described. Sections through the tips of the epithelial cells 

 of the peduncle and also sections sagittal to the axis of these cells 

 give sections like Figs. 25 and 26. I, therefore, conclude that this 

 epithelium is a sensory flagellate epithelium like that of the clubs. 

 Nerve tissue and unstriped muscle fibers underly the epithelium of 

 the peduncles. Glaus and Conant also describe a small ventral endo- 

 dermal tract of nerve tissue, which according to Conant is connected 

 with the endodermal nerve tissue found in the region of the radial 

 ganglia. 



To sum up, the epithelium of the club and the peduncle is a 

 flagellate sensory epithelium whose flagella are continued through 

 the cells as nerve fibers into the nerve tissue below. A priori, 

 judging from the mass of nerve tissue underlying the epithelium, 

 we should expect the epithelium to be one strictly sensory. What 

 sense it serves is difficult to surmise. In the physiological part of 

 this paper I suggested that it might be tactile, serving in connection 

 with the lithocysts in giving the animal sensations of space relations. 



Glaus mentions having seen patches of flagella on the epithelium 

 of the clubs. Schewiakoff supposes that his spindle-shaped sensory 

 cells have only a single flagellum, while his supporting cells have 

 many cilia. In the latter supposition he was evidently mistaken. 

 Conant (from an unpublished note) saw the flagella of the epithelium 

 on the living object and does not think that there could be more 

 than a single one to each cell. He also concludes from living speci- 

 mens squeezed out under a cover-glass, that there is only one kind 

 of cells in the ectoderm. 



Cilia and flagella extending into the cells to which they are 

 attached are described by a number of observers. 



