336 Mr. H. J. Carter on the Ultimate 
then expanded into the head, while the white crust was formed 
of the peculiar bacillary, sinuous, spined, minute spicule which 
Hancock gives (/. c.) as the characteristic one of the species, 
pore by the points of a bush of pin-like spicules, which, as I 
ave before stated, in the Clionide appear to be almost exclu- 
sively confined to these heads, the incipiently but densely 
spinous acerate spicules of this species being, as in G'rayella, 
almost as exclusively confined to the body of the sponge. 
Thus in the extension upwards of the ribs, composed of sar- 
code charged with spicules and based on the general structure 
of the sponge of which they thus formed tongue-like prolon- 
gations, I thought I saw the tentacles of a polype; but the 
clathrous netting together of their tips and sides with the in- 
vesting sarcode, and the rush of particlesin through the lattice- 
work thus produced, showed me that, however much these little 
retractile heads were like in form, they were not so in func- 
tion to the tentacular mouth of a polype. . In short, they did 
not act as the fringe of tentacles in Actinia and the Polypes, 
which are prehensile organs. "They acted as sieves to strain 
the water and prevent the entrance of particles which might 
be too large for the sponge-cells to enclose, or otherwise incon- 
venient for the sponge to receive. Thus in form they partly 
represented Polypes, but in function sponge-structure. 
In Hickel’s valuable paper (Annals, 7. c. p. 4) Leuckart is 
quoted as having stated that, “ if we imagine a polype-colony 
with imperfectly separated individuals without tentacles, sto- 
machal sac, and internal septa, we have in fact the image of a 
sponge with its large * water-canals' opening outwardly.” 
That is to say, in short, “ we have only to pick out the polypes 
of a polype-colony to have a sponge.” 
After this, at p. 10 (op. cit. l. c.), Hiickel alludes to cer- 
tain “ fine apertures in the skin [of corals] usually perceptible 
only through the microscope,” which he considers deserving 
the term “incurrent apertures” designed for respiratory 
purposes just as much as the pores of the sponge; but he 
previously admits that 4 the part played in the process by the 
cutaneous pores of the corals is unfortunately still as good as 
own. 
