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Structure of Marine Sponges. 341 
Still further, in reference to this subject, I might add that 
I have twice found a living specimen of Halichondria panicea 
here, of a lilac colour, which, on being torn to pieces, was 
found to be densely charged with minute spherical capsules, 
1-3000th of an inch in diameter, so like the sporidia of the 
Myxogastres that, as I have before stated in the * Annals’ 
(vol. v. p. 320, May 1870), but for the presence of the spi- 
cules and the specimens being fresh and living, I should have 
concluded that these cells came from one of the Myxogastres, 
and did not originally belong to the sponge. Could these 
have been the true sexual ova of the sponge? By develop- 
ment they would, of course, lose their homogeneous appear- 
ance, and become granuliferous. i 
aving endeavoured to show the near relationship which 
exists between the Sponges and the compound Tunicata, and 
the still nearer one which exists between the Foraminifera 
and Corals, I have only now to add a word or two in conclu- 
sion, on the real nature of the animal of the Sponges abs- 
tracte : 
The only naturalist, to my knowledge, who has turned his 
attention directly to this all-important point connected with 
them is Prof. H. James-Clark, of Boston, to whose valuable 
memoir on the subject (republished in the * Annals,' vol. i. 
dio Feb. 1868) 1 have alluded at the commencement of 
this paper. 
The object of Prof. James-Clark is to gus that the mono- 
ciliated sponge-cell is a distinct flagellate infusorium, possess- 
ing an oral and an anal orifice respectively, in close approxi- 
mation, at the bottom of a funnel-shaped retractile expansion 
which surrounds the base of the cilium, and also a nucleus and 
two contracting vesicles; further, that this flagellated infu- 
sorium is in no sense whatever related to the Rhizopoda ; and 
that it is an aggregation or colony of such Infusoria which 
produces the “ true ciliated Spongie.” 
I cannot altogether endorse Prof. James-Clark’s views, as I 
have stated (Annals, vol. iv. p. 196, Sept. 1869); nor do I 
desire to dispute his conclusions here, my object in this com- 
munication being to point out facts which seem to me worthy 
of consideration, and to leave all hypothetical arguments in 
support of particular opinions to those who think them of 
more consequence than I do, merely observing that the amce- 
boid pseudopodia of the Foraminifera (Digfugia) and the cilium 
of the Flagellated Infusoria (Zrachelius trichophorus, Ehr., 
Astasia limpida, Duj.) appear to be combined in the Sponges, 
and that, while the former may lead on to the Polypes, the 
latter may be the initiative form of the Polyzoa and Tunicata. 
