No. 1.] ACTINIARIA OF THE BAHAMAS. 63 
angular brown spots upon the disc, each with its apex at the 
angle of the mouth, the base resting upon the margin. 
The stolons in section (Pl. IV., Fig. 16) are seen to contain a 
cavity into which numerous small mesenteries project from the 
wall, being arranged as in the body of the polyp. The stolons 
are evidently elongations of the column of a polyp; the polyp 
becomes as it were very much drawn out in its lower portion, 
which becomes attached to the surface of the rock and gives 
support to the upper portion, rising up at right angles to it. It 
is to be noted that the formation of new polyps by budding does 
not take place from the stolon, but from the base of the polyp 
proper ; z.e., from the region where the polyp joins the stolon. 
The polyps measure from 0.9 cm. to 1.25 cm. in height, and 
at the top about 0o.4cm. in diameter, tapering off somewhat 
below ; in contraction they are club-shaped. The outside of the 
column is covered by a well-marked cuticle (Pl. IV., Fig. 15, cz), 
to which foreign bodies, such as diatom frustules, etc., are 
attached. This cuticle is no doubt a secretion of the ectoderm 
cells (ec), which, in the specimens examined, seem to have 
become fused to form a vacuolated layer, in which are numerous 
nuclei and strands of granular protoplasm. The mesogloea of 
the column wall measures 0.06—0.08 mm. in thickness, becom- 
ing, however, thicker above, and presents the usual structure 
described by Hertwig (’83) and Erdmann (’85). The endoderm 
is thin, measuring only 8y—12, and is densely packed with 
“yellow cells.’ The general musculature of the column is 
very weak, the muscle cells forming an almost flat layer. The 
sphincter is imbedded in the mesogloea and is double, the column 
wall in contracted individuals being deeply constricted in that 
region between the two portions, as in the form figured and 
described by Erdmann. The upper portion is small, and has its 
muscle fibres running in many cases obliquely, so that a vertical 
longitudinal section does not show them cut across transversely ; 
the lower portion is long, extending down the column wall for a 
distance of about 5 mm. 
The tentacles are arranged in two cycles, and in the larger 
polyps number from 44 to 50. Their ectoderm does not possess 
the cuticle which occurs on the column, but is ciliated. The 
muscle layer is weak, but still somewhat stronger than that of 
the column wall. The mesogloea differs from that of column in 
