CALYCOSILVA CANTHARELLUS. 89 
to the clavules with twisted branch-rays of Farrea occa claviformis and the 
helonychhexasters above described. The discohexasters with spirally twisted 
end-ray verticils of Hertwigia falcifera, Rhabdopectella tintinnus, and Saccocalyx 
pedunculata and the clavules with similarly twisted branch-rays of Farrea con- 
volvulus on the other hand do not appear to be associated with regular, not 
twisted spicules of the same kind. 
In studying the question how these spirally twisted spicules have been 
produced I gained the impression that the parts of the living mass’ which built 
them must have changed their relative positions in a torsional manner during 
the growth of those rays or portions of rays which are spirally twisted in the 
full-grown spicule. In the case of the oxyhexasters, helonychhexasters, and 
clavules with spirally twisted branch-rays there is only one torsion-axis corre- 
sponding to one of the axes of the spicule, and in these the torsion seems to 
have affected the whole living mass uniformly. In the case of the discohexasters 
there are six torsion-axes of this kind, corresponding to the axes of the six main- 
rays, and six different torsional systems in the living mass. 
In speaking of the spirally twisted oxyhexasters of Rhabdocalyptus mollis 
which were found in some, but not in all specimens, Ijima ” says: ‘‘T am therefore 
disposed to consider them as of inconstant occurrence in the species. Possibly 
they are produced only under certain abnormal conditions.” Also in Calyco- 
silva cantharellus they have been found in one specimen only. Since, however, 
this was obtained together with the others destitute of these spicules in the 
same locality, at a considerable depth, where doubtless the environment was 
very monotonous, it is hardly to be supposed that the external influences acting 
on it could have been in any way different from the influences acting on the 
others. A spiral twisting of some of the spicules is, as the above statement 
shows, if not a frequent, still a widespread occurrence in hexactinellids. It 
seems therefore improbable that the spiral twist is produced through the influence 
of abnormal conditions, and to be considered as an abnormity. Neither can it 
be ascribed to obstacles preventing the (twisted) rays from growing in the 
usual direction, because, in the first place, there are no such obstacles, and 
because, in the second place, their presence could not affect, all the actually 
twisted rays of a spicule in the same way and induce them to curve round spirally 
in the same direction. 
1T use the expression “ living mass,” because I do not know whether these spicules are built by 
distinct cells, and if so, by how many, or by syncitia, and if so, how many nuclei or chromidia or other 
centres of vital action, these syncitia contain. 
27. Ijima. Studies on the Hexactinellida, IV. Journ. Coll. sci. Tokyo, 1904, 18, p. 266, 267. 
