86 ERNEST WAEREN. 



conspicuous lobes {s.iv.). The endoderm of the hypostome is 

 supplied with the usual deeply-staining secretory cells (figs. 5, 

 7, 8 s. c). The tall endoderm cells are not amoeboid to any 

 extent. 



Below the hypotome we pass into the digestive cavity 

 (fig. 5, d. c). Here the ordinar}^ endoderm cells are exceedingly 

 amoeboid, and are of very irregular outline (a. e.). Wedged 

 between the ordinary cells are special digestive or gland 

 cells {g. I.) which stain intensely with hsematoxylin and other 

 stains; also large cnidoblast cells are fairly abundant. At the 

 expanded basal region of the hydranth the endoderm is 

 markedly differentiated into three layers : (1), a covering 

 layer of somewhat short amoeboid cells (b. ep.) and gland 

 cells (fig. 5 n, gl. c.) which are separated by a kind of base- 

 ment membrane or mesoglea from (2), a middle-thick layer 

 of highly vacuolated cells {r. ed.) and (3), smaller less 

 vacuolated cells which lie in immediate contact with the 

 mesoglea {b. ed.). 



The covering layer of amoeboid cells marked b. ep. is 

 shown enlarged in fig. 5 a, and it is especially charac- 

 terised by containing in greater abundance than the rest of 

 the endoderm large granular masses enclosed in vacuoles 

 ipr.). These masses appear to escape from the cells and 

 pass down into the hydrocaulus, where a couple may be 

 seen, marked ^^r., in fig. 5. I suggest that these bodies are 

 to be regarded as masses of worked-up food material which 

 are being distributed to different parts of the hydroid. 



An open channel leads from the digestive cavity of the 

 hydranth into the coelenteron of the hydrocaulus (fig. 5,f. c/;.). 

 The upper portion of this channel is narrow, and is lined by 

 small amoeboid endoderm cells continuous with the layer of 

 covering cells on the floor of the digestive cavity (see fig. 12, 

 c. e.p.). As the passage approaches the diaphragm (fig. 5, d) 

 it greatly expands and is lined by long, flat, non-amoeboid 

 cells. The passage is greatly constricted as it passes through 

 the small aperture of the diaphragm. 



The basal or proximal tentacles arise from the margin of 



