544 W. WOODLAND. 
arise in one cell (fig. 39, ¢, e), but of this I am not absolutely 
certain, since the other cell may have been detached from the 
young triradiate or rod, and young stages are so few in number, 
at least im my material, that I cannot come to a definite opinion. 
Older stages, where the original triradiate or terminally- 
bifurcated rod has branched, with one, two, three, four, and 
perhaps more nuclei, are quite common (figs. 40, 41). Some 
of these superficial spicules which happen to be more deeply 
situated in the epistroma have their main branches joined 
peripherally into a ring which then bears knobs (fig. 42). I 
hope, in the near future, to be able to more definitely ascer- 
tain the development of these superficial spicules,’ and to 
settle what is rather an important question from a theoretical 
standpoint, viz. whether a triradiate spicule is capable of 
originating in a single scleroblast. I believe that in the 
Cucumarian epistroma it is capable of doing so, largely 
because so many of the adult superficial spicules only possess 
a single scleroblast, as shown in fig. 40. 
Previous LireRATURE. 
Previous literature relating to the subject of the present 
paper is rare. The first observations known to me, made by 
an undoubtedly competent authority, are those of Théel, the 
results of which were published in the Challenger monograph 
on the Hlasipoda in 1882. Théel attempted to study the 
development of the simple elongated spicules contained 
within the thin walls of the pedicels of young Oneirophanta, 
but owing to the rough methods adopted in the preservation 
of the material, no very definite results were obtainable. 
Théel’s theory, which was evidently suggested by an in- 
spection of the material, was that the sheath of the spicule— 
‘‘a thin membrane, which, when treated with hematoxylin, 
became deeply coloured and very manifest”’—was developed 
first, “the calcareous matters being subsequently produced 
by it.’ “The sheaths increase and gradually assume the 
1 See further in section on Thyone. 
