Experiments on the Noctiluca miliaris. 419 



cumstances of combination, of giving rise to the phaenomena 

 of phosphorescence. The experiments on which Matteucci 

 grounds his opinion, were no doubt very carefully conducted ; 

 yet it may be questioned whether a different result might not 

 be obtained, could a test of such extreme delicacy be rendered 

 applicable in this instance, as we are furnished with by Marsh's 

 apparatus in respect to arsenic. Whilst still upon this sub- 

 ject, I may mention that experimenting some years since with 

 a view to test the theory of the luminous matter of the glow- 

 worm being a natural phosphoric oil, and at the same time to 

 imitate artificially the experiment of Forster, I enclosed some 

 phosphoric oil in a delicate membranous sac, which I then 

 introduced into oxygen gas. The result however was any- 

 thing but favourable to Chaptal's theory, since the phospho- 

 rescence, which had been well-marked whilst in atmospheric 

 air, ceased immediately upon the immersion of the bladder in 

 oxygen. 



It has been supposed by many experimenters that vital 

 phosphorescence is remotely connected with, or dependent 

 upon, the action which is termed "insolation"; and although 

 we find experiments detailed by Matteucci which at first in- 

 clined him to this opinion, yet, on a more careful and exact 

 repetition of them, he was led to admit that " when the insect 

 is placed in its natural conditions with regard to temperature, 

 humidity, &c., and continues to be nourished, the phosphores- 

 cent matter is preserved independent of solar action," a con- 

 clusion with which the result of the observations made by 

 myself, in the case of the Noctilucae, entirely corresponds. 



In reverting here to the experiments on the Noctilucae, it 

 may be observed that the medium in which they live gave an 

 opportunity for certain experiments which cannot be obtained 

 in the case of the glow-worm — I refer more especially to the 

 influence of galvanism and electro-magnetism formerly de- 

 scribed. From the agency of the former however we have 

 seen little or no effect to be produced ; whilst the influence of 

 the latter appeared to be only of the nature of a powerful 

 stimulus, not dissimilar in its character from that produced 

 by the strong mineral acids. 



An experiment may also be mentioned here, a notice of 

 which, from its negative character, was omitted in its proper 

 place ; and is now briefly introduced lest it should be sup- 

 posed, from the omission, to have been overlooked — I allude 

 to the effect of temperature on the luminous sea-water. On 

 placing a bottle of the sea-water in a vessel containing com- 

 mon spring water at the temperature of 90°, no remarkable 

 effect or increase of light was to be observed ; and it has been 



2 E2 



