276 W. WOODLAND. 
seen, each apical cell acts in conjunction with its respective 
basal cell in order to produce a monaxon structure, but 
eventually this co-operation ceases, and the basal cell com- 
mences to secrete spicular substance round the base of the 
ray in order to consolidate it centrally. Now the three rays 
once affixed centrally, the shifting of the basal cell from the 
base of the ray (and in young stages the basal cell is, as 
forming part of the trefoil, always more or less radial in 
position) into an adjacent interspace (which, being inde- 
pendent, it is at liberty to do) above noticed, is rather 
advantageous than otherwise, but, at the same time, it in- 
volves the loss of that cylindrical disposition of the cell- 
\ | TEXxT-FIG, 1]. | 
 — 
Gielen er a 
substance relative to the ray that commonly obtains; hence 
the fact cited above (p. 249), that the basal cells of triradiates 
alone do not possess this conformation—the cell in forming a 
deposit to one side of the ray loses connection with the other 
and does not regain its cylindrical disposition when secon- 
darily migrating. 
Many other problems remain to be solved, but the solution 
of these, as of those above discussed, can only be satisfactorily 
accomplished by means of a comprehensive survey of the vast 
array of facts presented by the structure and bionomics of 
the numerous genera and species of calcareous sponges known 
to exist. 
