STUDIES IN SPICULE FORMATION. 235 
The triradiate spicules are fairly uniformly distributed in 
the substance of the sponge wall (the three rays of each 
Trxt-Fic. 1. 
[T=] 
Showing secondary forms of triradiates consequent on difference of 
localisation in the sponge. The top row represents spicules from 
the extremity of the oscular rim; the second row from the base 
of the oscular rim; the third row from the median region of the 
sponge body, and the bottom row from the base of the sponge. 
All these figures have been drawn with the camera lucida from 
the actual objects. 
spicule lying in its curved plane, and therefore not protruding 
at the sides), and, like the monaxons, assume a regular and 
