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Mr. IT. J. Carter’s Contributions 
optical delusion, so transparent is the cartilage against its 
point of contact with the opaque areolar sarcode. 
These “ folds ” and the composition generally of the 
“ coats ” of the canals forming the excretory system are well 
worth attention. In the first place, when at most only 
l-48th of an inch in diameter (fig. 4, e), they may, with a 
common lens, he seen to commence in the subdermal cavities 
(that is, just inside the cortex), and, joining each other, thus to 
become enlarged and finally terminate in the vents above men¬ 
tioned; while if the “vertical lines” of the fine reticulation 
which is seen in the translucent cortex under water (fig. 7, 6) 
are pore-tubes, as above suggested, which extend from the 
pores themselves on the surface to subdermal cavities as in 
other sponges, corresponding to those of the “ investing mem¬ 
brane ” of Spongilla ( c Annals,’ 1857, vol. xx. p. 25, pi. i. 
figs. 1, b 5, “ Ultimate Structure of Spongilla”), then 1 have 
already figured and described an excretory canal commencing 
in this way with the same kind of “folds” in Greyella cyatho- 
phora ( l Annals,’ 1869, vol. iv. pp. 192, 193, pi. vii. fig. 5, &c.). 
It may be questionable how far the longitudinal and trans¬ 
verse fibres of the excretory canal, together with those of the 
cortex, may not be the same—and the whole, bundles of mus¬ 
cular fibrillm ; for the fibres lie parallel to each other, and are 
not united as in “ elastic tissue.” 
Lastly, it may be conjectured that the cells of which the 
mucous layer or epithelium is composed were once monocili- 
ated, and that, when living, the action of the cilia was to 
propel the contents brought in through the pores &c. towards 
the vents respectively, so as to keep up that aqueous circula¬ 
tion which appears, while it brings in nourishment, to be also 
the process by which the respiratory and excretory functions 
of the sponge are accomplished. 
The cribriform patches of vents overlying a large cavity, 
which is the combined end of several excretory canals below, 
also seems to indicate that this arrangement was for the better 
closing of these vents—which in Spongilla I have shown to 
be the case, for a while, after taking food (“ Ultimate Struc¬ 
ture,” op. et tom. cit. p. 30). We may assume this also from 
the diaphragm sphincter of transparent sarcode often present 
and half-closed in the vents of the excretory canals of many 
sponges. As a necessary consequence, this should be attended 
by a closure of the pores also ; and this, too, has been demon¬ 
strated in Spongilla {Joe. cit.). 
How delicate and transparent must be the muscular fibrillfe 
in these diaphragms, if such should exist here ! and who can 
doubt it when observing the form and transparency of the 
