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. Petersburgh’ for 1838, and the article ‘“‘ Luminous Animals,” in Dr. Todd’s ‘ Cyclopzedia 
of Anatomy, by Dr. Coldstream, a gentleman well versed in such inquiries. Several very 
interesting observations on the phosphorescence of the Ci/ograda* 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 Medusze, 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 Cilograda. 
Most of the accounts of the phosphorescence of Medusze have reference to the higher or 
steganopthalmatous species only; nevertheless, at an early period the light 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 equorea” (Aiquorea Forskalina, Lamarck) was noticed by 
Forskal: “Rasa ligno, parum adeo in tenebris splendet.”+ Peron and Lesueur afterwards 
mentioned their Aquorea phosphorifera as possessing the luminous power. Tilesius observed 
it in Charybdea marsupialis ; Rathke, in his “ Oceania Blumenbachit.”t Macartney announced 
the Thaumantias hemispherica 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 Medusze mentioned by Macculloch, 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 octocostatum), “ Oceania micro- 
scopica,’ and Thaumantias lenticula and hemispheriea.|| 
The British naked-eyed Medusz in which I have observed phosphorescence are species 
of Turris, Oceania, Dianea, and Thaumantias. In no case have I seen it continuous or 
constant in any one species. In every mstance 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 Medusze, 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 Zhaumantias, Steenstrupia, 
and Lizxia, 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 hibernica 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 the ‘ 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. 
+ Fauna Arabica, p. 110. { Philosophical Transactions, 1810. 
§ Loudon’s Mag. Nat. Hist., vol. iii, 1830. || Berlin Transactions, 1832. 
