REPORT ON THE TETRACTINELLIDA. xciir 
If the Sponges are to be classed with the Metazoa (as so many spongologists appear 
to think they should) the question arises as to whether they should be included with the 
Ccelentera, as a class (Ganin), subtribe (Polejaeff), or phylum (von Lendenfeld), or 
whether they should form a group independent of the Coelentera? Vosmaer argues in 
favour of the latter alternative, as I did myself, and on the same grounds as Vosmaer, in 
1876,^ when I represented the relations of the two groups thus : — 
The Gastrula attaches 
itself by 
The oral pole The aboral pole 
Spongia:. Ccelentera. 
If to this character we add the presence of choanocytal cells, the role played by the 
mesoderm, and the invagination of the flagellated cells in the amphiblastula of the 
Calcarea (inversion of the germinal layers ?), it would appear that quite enough 
distinctions exist, and of quite sufficient importance, to justify us in assigning the 
Sponges to a place outside the Coelentera. 
We next approach the question whether the Sponges are to be included in the 
Metazoa or distinguished as a special subkingdom (Parazoa). Lendenfeld has an easy 
method of solving this problem : all a ni mals are divided into Protozoa and Metazoa, the 
Sponges are not Protozoa, therefore they must be Metazoa ; similarly the Metazoa are 
divided into Coelomata and Coelentera, the Sponges are not Coelomata and must therefore 
be Coelentera ; it is owing to the fact that this has been overlooked, more especially that 
the subdivision of the Metazoa has not been fully appreciated, that Biitschli and others 
have fallen into error. Now that Lendenfeld has pointed it out nothing can be clearer, 
and no one, as he remarks, “will raise any objection to the statement” “that the 
Sponges are evidently Metazoa and no doubt Coelentera.” Although perhaps after such 
a fundamental oversight Biitschli and I (for I err in good company) might be excused 
from discussing this subject further, I shall now proceed to show on what grounds I 
still maintain the existence of a separate subkingdom Parazoa. In the first place the 
Sponges are distinguished by the constant possession of collared flagellate cells ; these 
never fail, for no Sponge, notwithstanding the vast number which have been exhaustively 
studied, is known in which they become replaced by ciliated cells, like those which 
occur in the Coelentera and Turbellaria. On the other hand no animal, not a Protozoon, 
and in particular no Coelenterate nor Turbellarian, is known in which similar collared 
flagellate cells appear. 
^ This was soon after Carter’s discovery that the larva of Halichondria simulans attaches itself by the “ posterior ” 
extremity (Carter, Ann. and Mag. Nat. Hist., ser. 4, vol. xiv. p. 14, 1874). My view was printed in a Syllabus of 
Lectures on Biology, of which about 150 copies were distributed ; although not published at this time the same view 
was alluded to later in an Article on Spongiee, Cassell’s Natural History, p. 325, 1883. 
