352 BE. A. MINCHIN. 
to a fragment of a triradiate. scl.m. Two formative cells of a monaxon 
spicule, which has begun to be formed as a clear space (compare Figs. 2, 3, 
and 40n Pl. 17). Four collar-cells are seen. 
Fie. 46.—Section of the oscular rim, showing five cells of the dermal epi- 
thelium; im one of them a portion of the shaft of a monaxon spicule (m.sp.) is 
imbedded. ‘The two uppermost collar-cells (¢.c.) come into the section. 
Fie. 47,—Portion of a section of the oscular rim, showing four cells of the 
dermal epithelium; in one of them is embedded a monaxon spicule, which is 
cut across. 
Fic. 48.—Section of an early stage of one of the large, curved, barbed 
monaxons (compare Fig. 9 on Pl. 17). The section was thick; hence the 
spicule, which was placed obliquely in the section, is much foreshortened in 
the drawing. 
Fie. 49.—Portion of a section showing two cells of the dermal epithelium 
(d.ep.); a wandering cell (am.c.); two cells of a sextett (se/.) ; and six collar- 
cells, in one of which only the base is seen in the section; besides fragments 
of spicules. 
Fic. 50.—Portion of a thick section, showing a young quadriradiate; on 
the basal system five of the six formative cells are seen; the gastral ray (g.7.) 
projects between the collar-cells and bears an actinoblast with two nuclei 
(compare Figs. 24 and 28 on Pl. 17). 
Fic. 51.—Section showing a very young quadriradiate; five of the forma- 
tive cells of the basal system are seen, and the large, granular, gastral actino- 
blast (g.act.) with its single nucleus (compare Fig. 26 on Pl. 17). 
Fie. 52.—Young quadriradiate, intermediate in size between those drawn in 
the two preceding figures. Four formative cells of the basal system are seen, ° 
and the gastral actinoblast has two nuclei. 
Fie. 53.—Three collar-cells, drawn from a section, with a granular ex- 
cretory cell (ez.c.) amongst them. 
Fie. 54.—Section passing through a pore (P.). On the right of it are seen 
two dermal epithelial cells (d.ep.),a sextett (ser¢.), and a cell (p.c.) which may 
be either the principal portion of the porocyte, or a gastral actinoblast. 
Fie. 55.—Section showing a young triradiate embedded in its sextett of 
formative cells (sez¢.). 
Fre. 56.—Section through the lower part of the oscular rim. On the right 
an excretory cell (e.c.) is seen amongst the collar-cells; one collar-cell (c.c.), 
of which only the base appears in the section, has been filled in, to show the 
difference between its cytoplasm and that of the excretory cell. On the left 
is seen the gastral ray (g.7.) of a quadriradiate; near it is a dermal epithelial 
cell, which sends out a prolongation ensheathing the gastral ray. 
