264 ON THE ACTION OF LIGHT 



would they afford other and not unimportant proofs, towards 

 a certain knowledge of these remarkable substances, and of 

 the true position which they occupy amongst the manifold 

 works of Nature. 



NOTES. 



(1) This species is the Spongilla friahilis (Lamarck) ; 

 EphydatiaJluviatilisiliaimouvouiL); Halichondriajluviatilis 

 (Fleming) ; and Spongia fluviatilis (Linnaeus). 



(2) Having, in the summer of 1838, finished another expe- 

 riment on this head, I found, by placing some living speci- 

 mens of the Spongilla of different shades of green, — one of 

 which was a very deep green, — in a pan of water confined 

 to the dark, that the green colour gradually decreased, and 

 became much paler. I must also mention, that the colour 

 underneath all those specimens whose upper surfaces were 

 submitted to the full action of the light, continued to the 

 last perfectly greenless, by reason of the deprivation of 

 light. 



(3) I have lately repeated the same experiment with success. 

 On March 20th, 1838, I obtained some small greenless spe- 

 cimens of the Spongilla from under the same arch, and after 

 the expiration of sixteen days, they had received a clear, 

 though rather pale green colour. This change took place in 

 the light of a window, at a season when the sun shone but 

 little, and when its illuminating rays had only a small de- 

 gree of power. I ought to state, that all the masses of river 

 sponge, on which the above observations were made, were 

 free from any moss, or other vegetable, by means of which 

 the green colouring matter might, perhaps, be supposed to 

 have been communicated to those specimens. 



(4) I will take this opportunity of making known, that I 

 discovered in the summer of 1837 (August 24), among some of 

 the before-mentioned specimens of this Spongilla, the little 

 fresh-water Zoophyte called Tubularia repens by Gmelin, 

 Naisa repens, by Lamouroux, and Plumatella repens, by 

 Lamarck. I am not aware that it has ever before been found 

 in England, though Dr. Fleming gives the " Lochmill-loch, 

 Fife," in Scotland, as a locality for it. The elegant crystal- 

 line Polypes lived in great activity for several days. In 

 March, 1838, I again found a mass of these Poly paries : at 

 first, no Polypes were visible, and T, of course, fancied that 

 they were dead ; after three or four days, when the mass had 

 been placed in water in the window of a room in which there 

 was a fire during half the day only, two or three Polypes 



