150 W. WOODLAND. 
difficult to distinguish between them. The development of 
the Tethya spheraster in fact is essentially the same as that 
described by Keller! (18) for the spheraster of Chondrilla 
nucula. I may further mention that Miss Sollas (86) also 
failed to find any signs of calthrops, though plenty of 
globules, in the larva of Tethya ingalli. The single 
scleroblast which contains the initial granule divides as the 
spheraster increases in size, with the result that the adult 
spheraster possesses several cells; whether any of these are 
not division-products of the original mother-cell but are 
extraneous in origin, as Maas confidently thinks, I am unable 
to say, and I fail to see how it is possible to say without at 
least very special inquiry. 
With the above criticism on Maas’ work in connection with 
spicule formation I may include another and minor one. 
During my observations of the developing spicules of 
Esperella lingua I could never find more than one nucleus 
associated with each of the anisochelee in this species (fig. 18) 
whereas Maas (28) states that four nuclei occur in connection 
with each such spicule in Esperella lorenzi—a statement 
which I feel sure is incorrect. I have observed numerous 
rosettes in H. lingua, and in every case each anisochele only 
possessed one nucleus. In each rosette the anisochele were 
embedded at their inner extremities in a spherical mass of 
protoplasm which contained several nuclei, but all of these 
nuclei were quite distinct from those which belonged to the 
anisochele. The answer to the question as to how the aniso- 
chele rosette is formed is not as yet known. Carter (8), with 
others, supposes that the entire cluster of anisochele is 
derived from separate silica deposits initially present in one 
1 Or rather as Keller should have described it. Keller figures the spikes 
as arising successively on the surface of the siliceous globule, whereas, in 
reality, they arise for the most part simultaneously as small knobs which 
cradually assume the pointed form. The spicule is enveloped in one sclero- 
blast throughout its existence. The calthrops of Corticium candelabrum 
e.g. also originates in the same way—the granule developing four processes 
which elongate to form the four rays of the calthrops; also the chiaster, 
oxyaster, and sterraster of Geodia gigas, | 
