14 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
20 /x in length, 4-5 /x in thickness, with nearly spherical nuclei 4 or 
5 /x in diameter. Their deep ends are tapering, so that the layer 
merges into the underlying connective tissue without causing any 
sharply defined line of separation to appear in sections. In the 
middle and posterior parts of the body the height of these cells is 
less than in the anterior part. 
Among the ordinary epithelial or supporting cells just described are 
slender sensory cells, the deep ends of which are undoubtedly in 
connection with a subepithelial nerve plexus consisting of numerous 
large, stellate, ganglion cells (cl. gn .), each of which gives off several 
fibers. Bundles of nerve fibers pass from this nerve plexus through 
the connective-tissue layer to the layer of nervous tissue which 
immediately underlies it. 
The epidermis of the tentacles is thicker than that of the rest of 
the body-wall. It consists of ordinary supporting cells (cl. sst.), 
nerve cells, and numerous gland cells, which are similar to the tubular 
gland cells which Hamann has found in Synapta. The supporting 
cells (Plate 2 , figs. 6, 7, 8, 15) do not differ from those of the body- 
wall, except in the unusual length of those found on the four tenta¬ 
cular processes. Here they may attain a length of 50 g. 
The nerve cells (Figs. 9 and 15, cl. sns.) are similar to those in 
Synapta described by Hamann. The nucleus lies between the middle 
part and the superficial extremity of the slender cell. The peripheral 
end tapers to a fine point, and the deeper part is prolonged into a 
slender fiber. 
The tubular gland cells (Figs. 10 and 15, gl. tbl.) are 48-50 /x in 
length with a nucleus, about 4 x 5 /x in dimensions, situated near 
the middle of the cell. The peripheral part of the cell is tubular or 
ovoid, and between this part and the nucleus a constriction can be 
seen in most cases. The nucleus occupies a swollen portion of the 
cell, the deep end of which tapers rapidly from the region of the 
nucleus. The granular contents of the peripheral part of the gland 
cell stain deeply with haematoxylin, and thus these cells are sharply 
differentiated from other parts of the epithelium. Whereas gland 
cells are found in small numbers over the whole anterior part of the 
body including the buccal region, in the tentacles, especially upon 
the finger-like lobes, they are exceedingly numerous. I have never 
found them in groups connected with a nerve bundle, such as 
Hamann describes in Synapta, although the groups of sensory cells 
in Caudina, presently to be described, occasionally contain a gland cell. 
