Akademie der Wissenschaften zu Berlin. 411 



them to heat ; he punctured, cut, and tore them, but in spite of all his efforts, 

 never could discern the smallest spark of light. The ovaria of some were 

 full, and of others undeveloped. The same remarks apply to the undoubted 

 specimens of Medusa aurita which he obtained in the Red Sea. Humboldt, 

 in his voyage to the Brazils in 1814, caught several specimens off Teneriffe, 

 which were peculiarly luminous. On being laid on a tin plate, they emitted light 

 when it was struck. The same phenomenon occurred the moment that the 

 wires of a galvanic battery were joined. Ehrenberg therefore supposes, from the 

 totally different results which .he always obtained, that what is called the Me- 

 dusa aurita of the Atlantic must be a very nearly allied species to that found 

 in the East Sea, and the Red Sea, though hitherto called by the same name. 

 After a violent storm at Heligoland in 1835, numbers of Medusa was thrown 

 ashore, and amongst others, Cyanea capillata, Chrysaora isoscela, Cyanea La- 

 marckii, and a small new species, to which Ehrenberg gave the name of Cyanea 

 Heligolandia. None of them emitted any light, but thinking that a difference of 

 temperature might have occasioned the disagreement of his own observations 

 with those of Humboldt, they were placed in warm water, but without effect. 

 No infusoria were found in the luminous sea water at Heligoland, but quantities 

 of morsels of gelatinous matter, often torn and ragged, which emitted light, and 

 small gelatinous globules, with jagged edges, occurred similar to those before de- 

 scribed, which he obtained in the Red Sea. They all emitted similar sparks, on 

 pouring a portion of brandy, spring water, or hot sea water upon them. They 

 were evidently alive, swam slowly, and amongst them he easily detected numbers 

 of Medusa or Noctiluca scintillans. On shaking the glass containing them a 

 few sparkled, but not all. During his stay at Heligoland, the author often ob- 

 served, as it were, chains of luminous matter floating about in the sea, some of 

 which, with some difficulty, he succeeded in obtaining. He then proceeded im- 

 mediately to his house, and examined them without delay. They proved to be 

 masses of luminous Medusa, detached and torn by the violence of the sea, but 

 he found that they continued to emit light, only as long as they retained vitality. 

 Some of these fragments will live for a week, while others die, and are decom- 

 posed in a very short time. He has no doubt that the difference of opinion 

 which exists on this branch of the subject has arisen from collectors having 

 delayed to examine such luminous water, till the morning after it was taken, 

 when the torn particles may be already dead, and incapable of emitting any 

 other light than what proceeds from decaying fish, &c. The sea animal whieh 

 gives out the brightest light of all is the Nereis cirrigera, one of the Annellides. 

 They live together in large masses, in branching sea- weed, and when portions 

 of it are thrown ashore they continue to live, and shine with great brilliancy for 

 many days. It is difficult, from the momentary nature of the spark given out 

 by the Medusa and infusoria, to perceive in what way the light is generated. 

 In the Photocharis, it is very visible. On each side of its feet, it is furnished 

 with two fleshy threads, the upper one longer than the other, and not so thick 

 but strongly resembling each other in their internal structure : a circulation of 

 globules of blood is perceptible in each. The light always proceeds from these 

 cirrhi, and particularly from the under or thicker one, which lies between the 

 rough tubercles of the foot, and the upper one. A few detached sparks first 

 appear on each cirrhus, which gradually increase till they are both illuminated. 

 They then proceed over the back, till the whole animal shines with a greenish 



