12 PHOSPHORESCENCE. 



and those of our readers who may wish for fuller information on the general question, would 

 do well to consult the excellent essay of Brandt, in the 'Transactions of the Imperial Academy 

 of St. Petershurgh' for 1838, and the article "Luminous Animals," in Dr. Todd's 'Cyclopaedia 

 of Anatomy,' by Dr. Coldstream, a gentleman well versed in such inquiries. Several very 

 interesting observations on the phosphorescence of the Cilograda* have also been published 

 by authors, both British and foreign ; but these are foreign to my subject at present, as I 

 wish to confine the discussion mainly to the naked-eyed Medusse, and intend on a future 

 opportunity to treat of the Beroe tribe in full, having accumulated abundant new materials 

 for an essay on the British Ciliograda. 



Most of the accounts of the phosphorescence of Medusae have reference to the higher or 

 steganopthalmatous species only ; nevertheless, at an early period the hght given out by naked- 

 eyed species attracted attention, for we find in the middle of the last century the phospho- 

 rescence of one of them (" Medusa microscopica" — probably a young state of the Saphenia 

 dinema of modern authors) attracted the attention of the observant Slabber. Previously, the 

 phosphorescence of " Medusa eequorecC {Mquorea Forshalina, Lamarck) was noticed by 

 Forskal : " Rasa ligno, parura adeo in tenebris splendet."t Peron and Lesueur afterwards 

 mentioned their ^quorea phosphoj'ifera as possessing the luminous power. Tilesius observed 

 it in Charybdea marsupialis ; Rathke, in his " Oceania Blumenbachii"% Macartney announced 

 the Thaumantias hemisphcBrica to be an active cause of the luminosity of the sea on our own 

 coasts, and detailed some interesting experiments which I shall presently have to cite. Among 

 the twenty phosphorescent Medusae mentioned by MaccuUoch, it is probable that several were 

 species of this division. One of the forms figured by Baird as a cause of phosphorescence in 

 tropical seas§ appears to be a Sarsia. Ehrenberg observed this phenomenon in Oceania 

 pileata, " Melicertum campanulatum" {Stomobrachium octocostatuni), " Oceania micro- 

 scopica," and Thaumantias lenticula and h,emisphcericaJ\ 



The British naked-eyed Medusae in which I have observed phosphorescence are species 

 of Turris, Oceania, DiancBa, and Thaumantias. In no case have I seen it continuous or 

 constant in any one species. In every instance the light has been given out only under 

 circumstances of irritation, and not always even then. Thus, on the 27th of July, 1845, when 

 in the Zetland Islands with Mr. M'Andrew, we collected myriads of small Medusae, and 

 placing great numbers in a basin of sea-water, irritated them by many annoying devices, 

 but though the vessels were charged with individuals of Thaumantias, Steenstrupia, 

 and Li%%ia, active and in good health, no light was given out ; nor could this arise from any 

 peculiarity of conditions in the vessel or contained water, for individuals of the ciliograde 

 Mnemia norvegica {Bolina hihernica of Patterson) gave out flashes of vivid bluish light, so 

 as at times to illuminate the whole vessel. This experiment was often repeated with the 

 same result, though at the same season in the following year, the not giving out light was the 



* The essays of Mr. Robert Patterson, in tlie ' Transactions of the Royal Irish Academy,' should 

 especially be consulted. I may here mention that such members of the Ray Society as have not 

 attended much previously to the subject of this essay, could not prepare themselves better for a prac- 

 tical study of it, than by consulting the admirable little ' Zoology for Schools,' by the valued friend just 

 mentioned. 



t T'auna Arabica, p. 110. % Philosophical Transactions, 1810. 



§ Loudon's Mag. Nat. Hist., vol. iii, 1830. || Berlin Transactions, 1832. 



