MATERIALS FOR A MONOGRAPH OF THE ASCONS. 321 
oscular rim above the limit of the collared gastral epithelium, 
I was unable to find actinoblasts upon them in sections, and it 
appeared to measif the gastral rays in this region were formed 
directly by the activity of the dermal epithelium lining the 
interior of the oscular rim (figs. 56, 68). My observations, 
however, are not sufficiently extensive to prove this point to 
my satisfaction. 
V. Deretict Spicutes In LEUCOSOLENIA COMPLICATA, 
In L. complicata I found frequently abnormal spicules 
which were evidently deformed triradiates or quadriradiates, 
and which were situated close to the dermal surface (figs. 30 
—36). Some had no cells attached to them, others had one 
or more cells, in one case (fig. 36) as many as four, but never 
the full number of six or seven found on normal spicules. 
These pecuhar bodies appear to me to be spicules which 
for some reason have. become arrested in their develop- 
ment and abandoned by their formative cells at an early 
stage in their growth, and are about to be extruded from 
the sponge. In one case the appearance seen (fig. 35) suggests 
that the formative cells were in the act of migrating from 
the spicule. ‘The peculiar forms of these spicules appear to 
be due to the fact that one or more of the formative cells may 
adhere to the spicule for some time, and continue to secrete 
calcite. Figs. 30 and 34 suggest this interpretation strongly. 
When all the cells have left them they become mere derelicts, 
which react as foreign bodies and are cast off. 
If my interpretation of these peculiar bodies is correct, they 
afford a certain analogy with the formation of the large 
monaxons of certain Clathrinide. AsIhavestated above, 
I found four formative cells on the monaxons of an undeter- 
mined species of Clathrina; this observation, by com- 
parison with the primary monaxons, indicates that the big, 
secondary monaxons of Clathrinide are biradiates, that is 
to say, are equivalent each to two rays of a triradiate, a view 
which I have maintained elsewhere (1905[8]) for those of 
