MED 
lindrical; truncated at one extremity, and rather conical 
at the other. This, which is one of the mod brilliant of 
the whole tribe of luminous creatures, was lately difco- 
•vered by M. Peron in the Atlantic Ocean. He created a 
new genus for it, of which this is the only fpecies yet 
difcovered, and which he calls Pyrefoma Atlanticum. The 
body is hollow, and does not contain any organ, except a 
very delicate net-work of vefl'els, which is fpread over the 
internal furface of the cavity. The circular aperture, or 
mouth, is furrounded internally by a number of tubercles. 
The external furface is ftudded with fome thick elongated 
tubercles, and others of a (mailer fize : they are the prin¬ 
cipal feat of the light, and fhine like polifhed diamonds. 
The interior of the fubftance of the body contains a num¬ 
ber of fmall elongated glands, which are alfo more lumi¬ 
nous than the tranfparent part. The colour of this ani¬ 
mal when at reft, or after death, is an opalein-yellow mixed 
with a difagreeable green ; but, during the contractions of 
its body, the creature appears, as it were, to kindle, and 
becomes of the red colour of fufed iron; it afterwards 
jsafles through different tints, as aurora, orange, green, 
and azure blue, according to the ftrength of its illumina¬ 
tion. When at fome depth in the fea, it gives the ap¬ 
pearance of a red-hot bullet; but, when floating on the 
furface of the waves, it refembles a cylinder of incandef- 
cent iron. It was obferved to perform regular and alter¬ 
nate motions of contraction and dilatation. The light is 
evolved during the contraCtile motions ; and thefe may be 
excited irregularly, by touching the animal, or merely by 
agitating the waterin which it is contained. The pyrefoma, 
like all the other luminous marine animals, exhibits no 
light after death. Annales du Mufeum d’HiJloirc Nalurelle , 
*4 Cahier. 
48. Medufa fcintillans: above fpherical, beneath flatted ; 
extremely fmall. We have obferved that Mr. Macartney 
firft met with thefe animals at Herne-bay, Kent. Having 
obferved the fea to be extremely luminous for feveral 
nights, he had a confiderable quantity of the water taken 
up. When perfeftly at reft, no light was emitted ; but, on 
the flighted: agitation of the vefl'el in which the water was 
contained, a brilliant fcintillation was perceived, particu¬ 
larly towards the furface; and, when the vefl'el was fud- 
denly ftruck, a flafli of light iffued from the top of the 
water, in confequence of fo many points fhining at the 
fame moment. When any of thefe fparkling points were 
removed from the water, they no longer yielded any light. 
They were fo tranfparent, that in the air they appeared 
like globules of water. They were more minute than the 
head of the fmalleft pin. Upon the flighted: touch, they 
broke and ,vanifhed from the fight. Having ftrained a 
quantity of the luminous water, a great number of thefe 
tranfparent corpufcles were obtained.upon the cloth ; and 
the water which had been ftrained did not afterwards ex¬ 
hibit the leaft light. He then put fome fea-water that had 
been• rendered particularly clear, by repeated filtrations, 
into a large glafs, and having floated in it a fine cloth, on 
which he had previoufly colleCfed a number of luminous 
points, feveral of them were liberated, and became dif- 
tinftly vifible in their natural element, by placing the glafs 
before a piece of dark-coloured paper. They were ob¬ 
ferved to have a tendency to come to the furface of the 
water; and, after the glafs was fet by for fome time, they 
were found congregated together; and, when thus col¬ 
lected in a body, they had a dufky ftraw-colour, although 
individually they were fo tranfparent as to be perfeftly m- 
vifible, except under particular circumftances. Their 
fubftance was indeed fo extremely tender and delicate, chat 
they did not become opaque in diftilled vinegar or alcohol, 
until immerfed in thefe liquors for a confiderable time. 
On examining thefe minute globules with the microfcope, 
he found that they were not quite perfeft fpheres, but had 
an irregular depreifion on one fide, which was formed of 
an opaque fubftance, tiiat projefted a little way inwards, 
producing fuel) an appearance as would arife from tying 
Voi.» J£Y. No. 1020, 
USA. SI 
the neck of a round bag, and turning it into the body. 
The motions of thefe creatures in the water were flow and 
graceful, and not accompanied by any vifible contraftioa 
of their bodies. After death they always fubfided to the 
bottom of the vefl'el. From the fparkling light afforded 
by this fpecies, he gave it the name of Medufa fcintillans. 
The Medufa fcintillans almoft conftantly exifts in the 
different branches of Milford-haven that are called pills. 
Mr. Macartney fometimes found thefe animals collefted 
in fuch vaft numbers in tbofe fituations, that they bore a 
confiderable proportion to the volume of the water in 
which they were contained; thus, from a gallon of fea- 
water in a luminous ftate, he ftrained above a pint 
of thefe medufte. The fea^ under fuch circumftances 
yields more fupport in fwimming, and the water taftes 
more difagreeably than ufual; probably the difference of 
denfity, that has been remarked at different times in the 
water of the fea, may be referred to this caufe. MrT Ma¬ 
cartney concludes that the Medufa fcintillans is the ufual 
caufe of the luminous appearance of the fea, not only 
around this country, but in other latitudes. Befuies the 
places already mentioned, lie has found this fpecies on dif¬ 
ferent parts of the coafts of Suffex, at Tenby, and in the 
bays of Dublin and Carlingford in Ireland. Many writers, 
he obferves, have miftaken this fpecies of Medufa for the 
Nereis noftiluca ; and fome navigators have aftually de- 
feribed the Medufa fcintillans without being aware of its 
nature. Mr. Bajon, during bis voyage from France ta 
Cayenne, collefted many luminous points in the fea, 
which he fays, when examined by a lens, were found to 
be minute fpheres. They difappeared in the air. Dr. le 
Roy, in failing from Naples to France, obferved the fpark¬ 
ling appearance of the lea which is ufually produced by 
the Medufa fcintillans. By filtering the water, he fepa- 
rated luminous particles from it, which he preferved ift 
fpirits of wine : they were, he fays, like the head of a pin, 
and did not at all refemble the Nereis noftiluca, deferibed 
by Vianelli ; their colour approached a yellow-brown, and 
their fubltauce was extremely tender and fragile. Not- 
withftanding this ftriking refemblance to the Medufa 
fcintillans, Le Roy, in confequence of a preconceived 
theory, did not fuppofe what he faw were animals, but par¬ 
ticles of an oily or bituminous nature. 
The minute globules feen by Mr. Langftaff in the In¬ 
dian Ocean, in all probability, were the fcintillating fpe¬ 
cies of Medufa; on his feeing fome of thefe animals that 
had been preferved in fpirits, he entertained the fame 
opinion. 
Profefl'or Mitchell, of New York, found the luminous 
appearance on the coaft of America, to be occafioned by 
minute animals, that, from his defeription, plainly be¬ 
longed to this fpecies of Medufa ; not with Handing which, 
he fuppofed them to be a number of the Nereis noftiluca. 
Phil. Mag. vol. x. 
To conclude. The light of the fea is now fuppofed to 
be always produced by living animals, and mo ft frequently 
by the prefence of the Medufa fcintillans. When great 
numbers of this fpecies approach the furface, they fome- 
times coalefee together, and caufe that fnowy or milky ap¬ 
pearance of the fea, which is fo alarming to navigators. 
Thefe animals, when congregated on the furface of the 
water, can produce a flafh of light, fomewhat like an elec¬ 
tric corrufcation. When the luminous Medufa are very 
numerous, as frequently j^appens in confineu bays, they 
form a confiderable portion of the mafs of the fea, at which 
times they render the water heavier, and more naufeous 
to the tafte ; it is therefore advifeable to always (train fea- 
water before it is drunk. 
MEDU'SA, f. in botany, a genus of the clafs mona- 
delphia, order polyandria. Generic characters—Calyx : 
perianthium inferior, permanent, of five, ovate, hairy, in¬ 
curved, fpreading, leaves. Corolla : petals five, ovate- 
oblong, curved, indexed, afterwards refiexed towards the 
top, longer than the calyx. Stamina ; filaments five, 
G thread- 
