Knowledge of the Spongida. | 105 
on the beach some time before they were picked up for preser- 
vation. 
Pigmental Cells and Origin of the Sponge-Ovule. 
(Pl. IX. figs. 3-9.) - 
The so-called “ pigmental cells,” which are by no means 
confined to the order Ceratina, are in most species of Luffaria, 
as well as in Aplysina, striking objects under the microscope, 
from their dark opaque carmine-purple colour, sharply defined 
outline, and compressed elliptical or globular form, averaging 
about 1-2000th inch in diameter (fig. 3, a); but in a dried 
specimen of a digitate branched species of Luffaria from the 
West Indies, in the British Museum (which is of a pinkish- 
brown tint), as, indeed, in the well-preserved specimen in 
spirit from the Levant, presented to the British Museum by 
Admiral Spratt, they are not so deeply coloured, although in 
other respects they present the same appearance (fig. 3, d) ; 
while in the Kuropean species of Aplysina, viz. A. carnosa 
and A. corneostellata, they are not only still lighter, but much 
less defined in their outline, possessing an elongate irregularly 
stellate form, in which the ray-like processes of the cells, 
more or less prolonged into thread-like forms, seem to be 
connected with each other. This is well seen in a large 
globular well-preserved specimen in spirit of the “ fine 
Turkey sponge” of commerce (Spongia officinalis) from 
the Black Sea, where, on the upper surface, they are dark 
purple in colour, becoming colourless towards the base; and 
in another, but dry specimen, of the same kind of sponge from 
theWest Indies, onwhich the dermal sarcode is absolutely black, 
the colour fades off gradually where extended into the sarcodic 
lining of the larger excretory canals, until, beyond a certain 
distance inwards, it disappears altogether, thus apparently indi- 
cating that, as in plants, the colour is deepest where the cells 
are most exposed to the light, and vice versd: yet this can 
hardly be the case always; for the dark-purple pigmental cells 
are almost as abundant in the flesh of Aplysina purpurea and 
Ianthella (which will presently be described) internally as in 
the dermal sarcode. 
In no instance have I found the pigmental cells so large 
or so defined as in Séelletta aspera and Dercitus niger (fig. 8), 
where they are elliptical or globular, and average 1-170th 
inch in diameter, contain a large colourless nucleus (fig. 8, a), 
and are otherwise filled with a great number of brown spherical 
granules (fig. 8,5), each of which is also nucleated and aver- 
ages 1-6000th inch in diameter (‘ Annals,’ 1871, vol. vii. 
pp. 7 and 4 respectively, pl. iv. figs. 14 and 6). The “gyra- 
Ann. & Mag. N. Hist. Ser. 5. Vol. viii. 8 
