Knowledge of the Spongida. 107 
same unit modified to meet their respective requirements 
(figs. 5,6). Hence it has appeared to me that while the cells 
(spongozoa) of the ampullaceous sacs (Geisselkammer) are 
uniciliate and take in food, there may be others scattered 
through the parenchyma which have no cilium and are more 
particularly ova-bearing, whereby the presence of the ova in 
the midst of the parenchyma, and not in the ampullaceous 
sacs, might be explained. That there are sponge-cells there 
under an ameeboid form (that is, without cilium), but with 
pseudopodia, which are interunited and capable of taking in 
food (carmine, fig. 7), has been pointed out by Metschnikoff 
in Halisarca Dujardinit (Zeitschritt f. wiss. Zoologie, Bd. xxxil. 
p- 372, Taf. xxi. fig. 4), after which my illustration is taken. 
The presence or absence of the cilium in the sponge-cell 
(spongozoon) is of no account; for, although provided with 
one when first liberated under water from the ampullaceous 
sac, the cillum may be seen to soon shrink back into the cell 
itself, which in its turn supplies the locomotive power by 
polymorphism, creeping about like an Ameba. This power 
of being able to put forth or retract the cilium I have long 
since pointed out in Acineta tuberosa, Khy. (‘ Annals,’ 1865, 
vol. xv. p. 287, pl. xu. figs. 9-11), as being worth remem- 
bering in a physiological point of view generally. 
Returning once more to the “ pigmental cells,” it is re- 
markable that, although chiefly confined to the surface and 
outer part of the large excretory canals, they are not always 
so; for in Janthella, as will be seen hereafter, they are not 
only present in the sarcode generally, but also enter largely 
into the composition of the horny fibre, both the dermal sar- 
code and the fibre being analogous in their skeletal uses 
according to the requirements of the case—thus affording an 
external skeleton in Geodia (the petrous crust), and an internal 
one in the fibrous sponges (viz. the “ fibre ”’). 
Moreover the colouring-matter, which appears to be born 
on the surface of the granules, often becomes separated from 
them and diffused throughout the sponge, leaving the granules 
themselves more or less colourless (in fact, just as they might 
be if not exposed to the light) ; or the diffusion might be con- 
fined to the sarcode of the pigmental body suspending the 
granules, and thus the former present a defined outline similar 
to a cell-wall, especially when dry. 
Aplysina fusca. (Pl. IX. fig. 11, af) 
There is another species of Aplysina in the Gulf of Manaar, 
of which I could only give a short description on account of 
the limited supply ; but it also appears to grow on the south- 
Qe 
