252 W. WOODLAND. 
trations of this condition have already been supplied in the 
above account of Sycon spicule formation, as e.g. by the 
respective positions of the basal and apical cells of triradiates 
corresponding to the thickened centre and elongated rays of 
the spicule, by the thickened distal end and secondary coating 
of monaxons corresponding respectively to the stationary 
condition and migration of the distal cell, etc., ete. 
Other calcareous sponges afford like evidence. Thus the 
“derelicts’”? of Leucosolenia complicata before men- 
tioned, the clubbed extremities of the triradiates of Clathrina 
clathrus (correlated, as Minchin shows, with the prolonged 
adherence of the apical cell), the gastral ray spikelets in 
Clathrina cerebrum corresponding to the fragmentation of 
the actinoblast nucleus, etc., etc., all illustrate the same law. 
It must be observed, however, that although it is necesary 
for the surface which is receiving fresh deposits of lime to be 
covered by a layer of “ calcoplasm,” yet the fact that the mass 
of protoplasm containing the nucleus is necessarily situated 
to one side of the growing ray does not affect the symmetry 
of deposition, as the figures of the Sycon monaxons show, and 
as is elsewhere abundantly illustrated! The process of 
spicule growth may, in fact, be compared in this particular 
with the building of a jetty by a multitude of labourers who, 
for a given reason, have moored a boat containing the 
provisions, timber, stores, etc., to one side. ‘lhe one-sided 
disposition of the boat and stores relatively to the jetty evi- 
dently will not interfere with the bilaterally-symmetrical 
1 The entire lack of influence exerted by the nucleus on the deposition of 
lime is well shown by the spherical lime deposits so often found in single cells, 
in which again the nucleus is necessarily placed to one side of the deposit. 
And if another illustration be required, it is to be found in the case of the bi- 
or multi-nucleated calcoplasm covering gastral rays and large clathrinid 
monaxons, in which nuclear-division is not accompanied by a corresponding 
fission of the entire mass of cytoplasm, as in ordinary cell-division, nor there- 
fore by any interference with the growth of the spicule. In short, the nucleus 
stimulates the cytoplasm, and the layer of cytoplasm next the spicule 
deposits the lime, and the conformation of the deposited lime is solely related 
to that of its immediate producer, 
