Mr. H. J. Carter on the Freshwater Sponges of Bombay. 97 
The contents of the dried seed-like body are yellow, and al- 
though the new sponge when it first grows from them appears 
to be white, yet, if its cells be examined under a high magnify- 
ing power, their granules will be found to be translucent and 
yellow, closely resembling, under transmitted light, the colour of 
chlorine. 
Sometimes the green colour of the yellow sponge is evidently 
owing to the presence of numerous solitary spherical corpuscules, 
at other times it is as evidently owing to the presence of an Osez/- 
latoria or to Diatomacee, but more frequently it appears to de- 
pend on the presence of some colouring matter in or about its 
cells or granules themselves. 
if some fresh cells of cinerea be examined under a high mag- 
nifying power, they and their contents will present the gray or 
lilac tint peculiar to the species, and in like manner the cells of 
yellow sponges which have become green would seem to indicate 
a similar position of their colouring matter, which in this instance 
however generally appears to depend on an extra tint of green 
added to the cell-granules only. 
Undoubtedly the sun has the power of turning the yellow 
sponges green when they are taken from the tank “and exposed 
in a glass vessel to his rays. At the same time the greater part 
of the sponges are exposed to the sun in their natural ‘habitations 
throughout the whole year, and yet, with the exception of fria- 
bilis (which i is always green, at least externally), it is only here 
and there that you find a portion of the others taking on that 
colour. Exposure to light again does not appear to have this 
effect on the small pieces of sponge grown from the seed-like 
bodies, if care has been taken not to admit the presence of other 
organisms, for they retain their white cotton-like appearance, 
although exposed to the sun for several days, 7. e. from the mo- 
ment they have become perceptible, up to the time that they 
perish from the want of nourishment in the distilled water in 
which they have been brought into existence. 
It is impossible therefore under these circumstances to say 
without further research, if the green colour is owing to an ad- 
ditional tint to the colouring matter of the cells or granules 
themselves, or to the presence of some foreign organism. Bory 
St. Vincent supposed it to be owing to the presence of Anabaina 
impalpabilis*, but when it is due to an Oseillatoria or to Diato- 
mace, or to solitary organic corpuscules, they are distinctly visi- 
ble ; the green colour however is fr equently present when neither 
can be observed. 
Among other experiments I instituted a set to ascertain if each 
species of Spongilla had its peculiar form of Proteus ; and for this 
* Johnston, Brit. Sponges, foot-note, p. 156. 
Am. & Mag. N. Hist. Ser. 2. Vol. iv. 
