250 W. WOODLAND. 
THe RELATION OF THE SCLEROBLAST TO THE SPICULE. 
If spicule preparations be stained with Kernschwarz for 
about ten minutes, the limits of the cell-substance become 
clearly defined, and the relationship of the form of the cell 
to the spicule is thereby rendered more evident than it is 
under ordinary conditions (the sheath of the spicule remain- 
ing though the calcareous matter becomes destroyed). Such 
preparations reveal the fact that the cells of monaxons, the 
apical cells of triradiates, and the cells of gastral rays form 
cylinders enveloping a portion (in the case of the two former) 
or the whole (in the case of the gastral ray) of the length of 
the ray on all sides (Pl. 15, fig. 50, shows monaxon cells thus 
treated; Pl. 14, fig. 38, shows a gastral actinoblast only 
slightly stained). On the other hand, the basal cell of 
triradiates (fig. 51) is not cylindrical in form, but simply 
adheres as an elongated mass to one side of the ray. The 
reason for this difference of conformation is one I shall 
presently point out (p. 276); at present I may again remark 
that this non-cylindrical disposition of the triradiate basal 
cell is perhaps responsible for the non-secretion of a secondary 
layer of lime in the course of its migration up the ray (p. 247). 
In the case of the cylindrical distal cell of monaxons, a 
secondary layer of lime is secreted during migration, as also 
previously mentioned. This simple method of defining the 
cell-limits just described effectually disposes of the idea that 
in all cases the spicule is entirely enyeloped by the distended 
cell-substance (e. g.see Maas’ figures). If this limited exten- 
sion of the cell-substance at first seems inadequate to account 
for the relatively large mass of the spicule secreted by it (as 
e.g. in the case of the apical cell of triradiates), it must be 
remembered that the secreted substance is wholly derived 
from the surrounding medium, and that the cell, like the 
familiar kettle on the fire, is only the secreting agency and 
will, if allowed sufficient time, deposit any amount of lime 
required, though, like the kettle, it becomes worn out in the 
