4 ERNEST WARREN. 



off irregularly; frequently they alternate, but sometimes they 

 appear to arise along a spiral line. The pedicel is indistinctly 

 annulated ; the ringing is more pronounced at the two ends, 

 but especially at the proximal end. The average length of the 

 pedicel is 2 mm. and the diameter is 80 ju. The perisarc is 

 about 14 fx in thickness. 



The coenosarc is typical except at the distal end close to 

 the hydranth. Here the coelenteron may be absent, and we 

 have simply an ectodermal layer with a central rod (PI. I, 

 fig. 8, en.) of modified endoderm cells with sparsely placed 

 nuclei and no obvious cell-outlines. Sometimes the endoderm 

 would appear to be wholly withdrawn, and there is left 

 simply an axial rod of substance indistinguishable from 

 mesoglea, and in cross-section the diameter may be less than 

 that of a nucleus of an ectoderm cell. 



Hydranth. — The body of the hydranth, in a moderate 

 degree of expansion, consists of a lower region forming an 

 inverted cone, and of a large projecting hypostome region 

 (PL I, figs. 3 and 9). Between the two portions there is a 

 ring of 16-33 tentacles. 



The dimensions of a moderately distended polyp with 

 twenty-two tentacles were : Total height '60 mm., Avidth 

 •40 mm. ; height of hypostome region '27 mm. ; depth of 

 subtentacular region '33 mm. ; average length of tentacle 

 supported by perisarc "80 mm., and diameter of tentacle 

 about 44 ju. 



The subtentacular region of the body forms an inverted 

 cone with a truncated apex where it joins the hydrocaulus. 

 The perisarc of this region forms a definite calyx, and is 

 continuous with the perisarc of the hydrocaulus. The floor 

 of the pei'isarc-cup is flat or somewhat raised by a slight 

 inpushing of the distal end of the hydrocaulus. In an 

 adult hydranth the calyx is not wholly filled by the body, 

 there being a well-defined empty space (figs. 3, 9, e. cy.) 

 between the ectoderm and the calyx-wall. With the edge of 

 the calyx, however, the ectoderm is in close contact. The 

 communicating aperture between the calyx and the hydro- 



