420 Metschnikoff on Germ-Layers. [May 
jelly, which serves to unite the members of a colony (Fig. 1, a). 
Here the amoeboid individuals remain, to divide and suffer further 
changes, which Kent interprets as evidences of sporulation 
(Fig. 2, s). Whether the adoption of the amceboid form, together 
with the migration into the jelly, is in any way connected with 
the state of nutrition, cannot be asserted at present, since the 
phenomena involved are quite unknown. In view of the fact 
that the sporulation is as yet an open question, I hazard a guess 
whether the numerous granules seen by Kent be not either bits 
of indigestible stuff about to be cast out, or else particles of food 
just taken in. It would be extremely interesting to study more 
closely the genus Protospongia (also the second Protospongia 
form described by Oxley, and consisting of numerous individ- 
uals), paying special attention to the phenomena of nutrition 
and propagation. Meanwhile we may accept the fact that this 
_ . Choano-Flagellate possesses two forms of individual, which nat- 
urally can pass one into the other,—a flagellate and an amceboid 
form, the latter of which is able to migrate from various points 
of the surface into the common mass of jelly. Protospongia 
: - ae thus offers such an unmistakable likeness to certain two-layered 
v — instance, the larva of Aplysina sulphurea de- 
* 
