UPON THE COLOUR OF THE RIVER SPONGE. 265 



appeared, protruding themselves from the extremities of the 

 tubes ; but at the end of a fortnight, or rather longer, to my 

 surprise, the Polypes became extremely numerous, and exhi- 

 bited themselves in full life ; thus showing that in the win- 

 ter, or cold weather, these little animals are torpid or inactive, 

 and keep entirely within their tubular dwellings ; but, on the 

 return of spring, when the temperatures of the air and water 

 are again sufficiently warm^ they revive and become lively. 



(5) The green in this Spongilla being increased by the 

 more powerful rays of light, as shown in the last-mentioned 

 experiment, affords a case extremely analogous to the results 

 of certain experiments made by Professor Daubeny on plants, 

 and which are stated by him in these words : — " from a few 

 experiments I have made on the secretion of green matter 

 in the leaves, I should be led to infer, in contradiction to the 

 results of Senebier, that the most luminous rays were most 

 influential ; the orange glass, whose chemical influence was 

 as four, whilst its illuminating power was as six, quickly im- 

 parting to the primordial leaves of beans which had just ap- 

 peared above ground, a bright green hue, whereas, under the 

 ammonio-sulphate, whose illuminating power was as two, 

 whilst its chemical influence was as five, they continued of 

 a pale yellow, scarcely indeed of a shade darker than in ano- 

 ther case where light was completely excluded. I have 

 made some experiments, with similar results, on the colours 

 of flowers, the intensity or depth of which appeared, also, to 

 depend on the brightness of the kind of light that had been 

 allowed admission to them." Again, the Professor observes, 

 — " Upon the whole, then, I am inclined to infer, from the 

 general tenor of the experiments I have hitherto made, that 

 both the exhalation and the absorption of moisture by plants, 

 so far as they depend upon the influence of light, are affected 

 in the greatest degree by the most luminous rays, and that 

 all the functions of the vegetable economy, which are owing 

 to the presence of this agent, follow, in that respect, the same 

 lawy — (See Professor Daubeny's paper, "on the Action of 

 Light upon Plants, &c." p. 158 and p. 163 in the Philoso- 

 phical Transactions for 1835). 



(6) Captain Sir Edward Parry, in his North Polar voyages, 

 used to raise quantities of mustard and cress in his cabin, in 

 small shallow boxes filled with mould, and placed along the 

 stove-pipe, for the purpose of giving a salad to the scorbutic 

 patients, " the mustard and cress," he tells us, " thus raised, 

 were necessarily colourless, from the privation of light ; but, 

 as far as we could judge, they possessed the same pungent 

 aromatic taste, as if grown under ordinary circumstances." — 

 (p. 133, Parry's Journal of his first Voyage, 1821.) 



