Affinities of the Sponges. 91 
Tn preceding paragraphs it has been pointed out that the 
function of the mouth, cavity, and canal-system does not affect 
their homology or homogeny ; and in the face of such forms 
as Prosycum, and the clearly demonstrable ectoderm and endo- 
derm and antimera of some forms and the general community 
of plan which Sponges and Corals exhibit (as even Mr. Kent 
allows in assenting to Protascus), it is not possible to maintain 
way of clearing up doubt as to the possible independence of 
these two systems ; but Professor Hückel's facts go a very long 
