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 Oscil- 

 latoria or to Diatomacece, 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 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, i. e. from the mo- 

 ment they have become perceptible, up to the tirnp 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 Oscillatoria or to Diato~ 

 macece, or to solitary organic corpuscules, they are distinctly visi- 

 ble ; the green colour however is frequently 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. 



Ann. §■ Mag, N. Hist. Ser. 2. Vol. iv. 7 



