with some Retnarks on the Nature of the Spongise Marinse. 387 



curious mannei- in which this diaphanous membrane is often puffed up, or 

 swells out from the surface of the gelatinous substance which it envelopes, 

 into little cones or roundish protuberances, as well as the manner in which 

 these latter are sometimes seen to burst or become pierced at their summit, 

 and to vomit forth a continuous stream of water. And the mode in whicfi I 

 have observed the River Sponge grow and extend itself is owing to this mem- 

 brane, namely, by its transj)arent edges gradually progressing over the stone 

 or whatever body it is attaclied to ; and so by tlie bulging out and rising up of 

 the same membrane, the variously formed lobes and the irregular eminences 

 upon its surface originate and increase in size. The same author has likewise 

 attributed the increase of the Lake Sponge to the like membrane ; for he 

 says, " Elle forme une expansion membraneuse qui s'accroît par ses bords de 

 la même manière que certaines Ulves*." 



The second, is the gelatinous or soft portion itself covered by that mem- 

 brane, which when magnified appears of much the same nature as tliat con- 

 tained within the membrane of the more fleshy kinds of leaves, and which 

 may be called the parenchymatous substance ; for example, I compared a 

 piece of that Sponge with a portion of the leaves of Crassula cocciuea, IIoi/u 

 carnosa, several of the Mesembryantherna, Sempervlva, Cacti particularly of 

 Cactus truncatus, Sfapelia variegata, &c. ; and placing one next to the other 

 on the glass under the microscope, I could distinctly perceive that the pulpy 

 or gelatinous material of the SpongiUa resembled the parenchymatous sub- 

 stance of those leaves, and appeared to be principally composed of numerous 

 pellucid globules. 



The third, the green chromule or colouring matter which is contained in 

 these globules, and seems to be nearly the same with that of the more fleshy 

 leaves of plants ; indeed, when squeezed on a piece of white paper, it stains it 

 of a green or yellowish-green coloiu' according as the specimen of the Sponge 

 itself is of a dark or light green. I have brought this evening for inspection 

 a sheet of white paper, on which I have pressed out the green chromules from 

 the leaves of several pheenogamous plants for the sake of comparing tliem 

 with the similar green matter from that Sponge, as well as some chromules of 

 different colours squeezed from the petals of certain flowers : all these it will 



* See Annales des Se. Nat., torn. xv. p. 212. 



