" The colour of the animals, when at rest or when moribund, was observed to be of an opaline yellow, mingled with a disagreeable green; but during the spontaneous contrac tions of the animals, and which were also easily excited at the pleasure of the observer, the body seemed to burn, becoming instantly like molten iron, with an extremely bright light ; but, as the phosphorescence again ceased, the colour of the animal passed suc cessively through a number of extremely agreeable, light, and varied tints, such as red, yellow, orange, green, and azure blue, the last shade being extremely lively and pure.
" Left to itself in a glass of sea-water, the Pyrosome exhibited at regular intervals of time a slight alternating movement of con traction and dilatation. In these movements, the phosphorescence was seen to be deve loped during the contraction, then to grow insensibly feebler, and entirely disappear, until in the next contractile movement it was quickly re-established.
"By often irritating the animal, either by touching it or by shaking the water in which it floated, the phosphorescence could be ex cited and maintained for a much longer time. Evidently dependent on the organisation and the life of the individual, after death, as is the case with all other phosphorescent marine animals, it could not be reproduced." We may remark that the observations made by Mr. F. D. Bennett *, who more than once met with shoals of P. atlanticum in lat. 1° 41' N., long. 11° 56' W., and lat. 4° S., long. 18° W., differ but slightly from M. Peron's notices of the same animal. The former observed, that when the specimens were taken in the hand from a vessel of sea water, the whole mass of the animal became instantly illuminated by myriads of bright dots, much resembling in hue the points on the wing-cases of the diamond-beetle ; and that the small specks of a brown or red colour, that were imbedded in the general tissue, and in termingled with the prominent, rigid, pearly tubercles, appeared to him to be the chief seat of the phosphoric light, frequently re maining bright, whilst the remainder of the body exhibited only its naturally white or yellowish hue—a hue which changed after death into a red tinge. In making a close
examination of the animal, Mr. Bennett re marked that no luminous matter was com municated from the surface of the animal to any fluid or solid in contact with it. But if the Pyrosoma were cut open and immersed in water, the brown particles that escaped diffused themselves through the fluid, and shone as numerous scintillations, independent of the perfect structure. General friction or contact was not essential to elicit the perfect light of the Pyrosome, since touching one small portion of the body was sufficient to produce a brilliant glow throughout the whole.
Mr. Bennett at the same time made the following observations on the effect of fresh water on phosphorescent marine animals. " Fresh water appears to act as a powerful and permanent stimulus on marine Noetilucw. Those that have intervals of repose from their phosphorescence immediately emit light when brought into contact with fresh water ; and this fact was strikingly exhibited in the Pyrosomata. When placed in a vessel of sea water and permitted to remain quiet, these Molluscs afforded no light, and, when touched, gleamed forth only as long as the irritating cause remained, and then gradually returned to their original state. When, however, the same creatures were placed in a vessel of fresh water, they never ceased glowing with their brightest refulgence until life was extinct, which was not until the lapse of several hours. When also the same Molluscs were mutilated, or so near death as to refuse to emit light upon irritation in sea-water, immersing them in fresh water produced at least a temporary revival of their brightest gleam."