254 Mr. W.S. Kent on the Affinities of the Sponges. 
position in the classification of organisms " than they now pos- 
sess, none would have been more open to convietion or wo 
have more warmly advocated its general acceptance than my- 
self; as it is, the step would be but one of retrogression. The 
day may arrive when an organism will be discovered em- 
bodying the characters of the two groups in such a manner 
that it will be diffieult to draw a line of demarcation between 
them, and their coalescence will be rendered necessary; but 
at present the merest tyro in zoology discriminates unhesi- 
tatingly between a Ceelenterate and a Protozoan, let the latter 
belong to the Spongiade, Radiolaria, or Amceboidea. 
ether Prosycum may or may not be regarded as the 
veritable stock-form of the Calcispongie must remain an open 
question, though maturer reflection would rather induce me to 
search for it among the allies of Clistolinthida. Even Prof. 
Hiickel himself admits that the Sponges without flue or oscu- 
lum are probably primitive sponge-forms. 
would also venture to express doubts whether it is among 
the Caleispongie we are to seek the form most closely con- 
necting the Coelenterata with the Protozoa, recent observa- 
tions on certain living Silicea and on Calcarea or Calcispongiz 
having afforded me the greater amount of evidence in favour 
of the former group. 
Mr. Lankester refers to Protohydra, a Hydroid Zoophyte 
devoid of tentacles, and consequently simply sac-shaped. Lar 
sabellarum, again, has only two tentacles; and there are num- 
bers of Anthozoa in which these appendages are almost alto- 
gether rudimentary ; but no difficulty has ever been expe- 
rienced in determining the ccelenterate nature of these animals. 
Such an organism as a simple sac-shaped Sponge, without a 
supporting skeleton of some kind or other, from the very na- 
ture of its substance, could not exist; as with the young lady 
of the period, tight lacing and whalebone must be represented 
by cue or reticulated fibres to preserve its shapeliness ; 
the Hydrozoon, on the other hand, is built up of firmer stuff, 
and is independent of mechanical means of support. 
These considerations suggest the following relative to 
Hiickel’s hypothetical sac-shaped Protascus. In the first place 
we must assume that organism to have been far simpler than 
either the existing Sponges or Corals which he supposes to 
Le Pb ee ee n np EM 
