Experiments on the Noctiluca miliaris. 415 



this difference of circumstance in the two instances, we shall 

 proceed to note some of the more remarkable points of con- 

 trast which they present to us, and which may be thus sum- 

 marily enumerated. 



As in the instances recorded by Matteucci and other ob- 

 servers, with respect to the glow-worm, so with regard to the 

 Noctilucae under consideration, the phosphorescence was found 

 to be remarkably increased hy oxygen ; in the former, how- 

 ever, not only was the light increased in brilliancy, but also 

 in duration ; whereas we have seen that the Noctilucae, con- 

 fined under an atmosphere of oxygen, died somewhat sooner 

 than those confined in a bottle containing atmospheric air. 



In hydrogen, glow-worms are found to lose their phospho- 

 rescence at furthest in about twenty-five or thirty minutes; 

 whilst the Noctilucae, under an atmosphere of this gas, con- 

 tinued to emit scintillations at the end of eight or nine days 

 from the commencement of the experiment. But it is in re- 

 spect to carbonic acid gas that the most remarkable contrast 

 is exhibited in the two cases. On placing glow-worms in this 

 gas. Prof. Matteucci found that in a few minutes the light en- 

 tirely disappeared; whereas, in the case of the Noctilucae, we 

 have seen that there is no agent which has the effect of in- 

 creasing the brilliancy of the light so powerfully as this gas, 

 at the same time that the bright phosphorescent glow formerly 

 described is rendered permanent for the space of fifteen or 

 twenty minutes. After the lapse of this time, however, this 

 gas proves as fatal to the Noctilucae, as to the glow-worm ; and 

 to the former, without the power exhibited by the latter, of 

 resuscitation of the light by the admission of atmospheric air. 



The effects of sulphuretted hydrogen gas appear to be pre- 

 cisely the same on the glow-worm and on the Noctiluca, both 

 being very speedily destroyed by it. 



Although those which have now been cited appear to be the 

 only instances which offer a fair opportunity for direct com- 

 parison, yet there are several other points which seem natu- 

 rally to demand notice in this place in connection with the 

 experiments formerly detailed. The phaenomenon of vital 

 phosphorescence has been regarded as presenting an analogy 

 to the function of respiration, if not connected with it. Thus, 

 in a paper in Tilloch's Magazine (vol. x) on the Phosphores- 

 cence of Ocean- water by Prof, Mitchell of New York, we 

 find the maintenance of the process of phosphorescence 

 ascribed to the presence of a supply of oxygen as conveyed by 

 the arterial blood, the process in fact being compared to re- 

 spiration as expressed in the following somewhat curious pass- 

 age : — " The light, then," says he, " which these marine ani- 



