552 W. WOODLAND. 
supply of properly-prepared material being strictly limited, I 
am only able at present to describe the scleroblastic develop- 
ment of spicules of the varieties (b) and (c) above enumerated. 
The development of the remaining varieties, however, doubt- 
less proceeds on the same lines. 
The youngest stages of the (b) variety of spicules I have 
been able to find are those represented by figs. 45 and 46, and 
these, it will be observed, are strictly of the more usual 
TEXT-FIG. 2. TEXT-FIG. 3. 
Cucumarian type. Even at this early stage the “stool” 
process, which points towards the exterior of the animal, is 
originating by shght protuberances at the bases of the 
bifurcations of the rod extremities. Spicules in which the 
second series of bifurcations has taken place (figs. 47 and 48) 
are, as also in the case of Cucumaria, of two classes—those 
possessing two scleroblasts and those possessing four. I 
have observed, in one fair-sized specimen of T’. fusus, at 
least four or five of these young spicules clearly with four 
scleroblasts attached. Since, as in Cucumaria, the majority 
of these spicules originate from only two cells (as is proved 
by the fact that in the majority of adult spicules only two 
