ae 
Sept. 17, 1885 | 
NATURE 
477 
moment as the ripple stretches outward, and then disappear ; or, 
still more vividly, when the plunging vessel sends the sparkling 
spray all around the bow. If, on removing the tow-net from 
such water at night it is suddenly jerked, the whole interior is 
beautifully lit up with a luminous lining, which glows brightly 
for afew seconds and then fades. I have been unable, nevertheless, 
to satisfy myself as to the phosphorescence of isolated examples 
of Ceratéwm, and Mr. Murray (who is inclined to follow Klebs 
in considering them algze), tells me that he has not been more 
successful. 
The most conspicuous member of the first group (viz. the 
Protozoa), however, is Woctéluca, which for a long time has 
been associated with luminosity in many seas. The minute size 
of this little transparent gelatinous sphere, which ranges from 
} to % of a millimetre, probably gave origin to some of the 
ancient views that the phosphorescence of the sea originated 
from the water, and not from any visible organisms. Amongst 
the first who clearly made known the relationship of this minute 
body to the phenomenon we are examining was M. Rigaut, a 
French naval surgeon, who examined it off various parts of the 
French coasts as well as off the Antilles, and pointed out in a 
memoir communicated to the Academy that the luminosity of 
the sea was caused by an immense number of what he termed 
little spherical polyps, about a quarter of a line in diameter 
(Fournal des Savants, tome xliii., February, 1770, pp- 
554-61). The observations of this acute French surgeon were 
followed up by many subsequent authors, amongst whom may 
be mentioned Baker, Martin Slabber, Abbé Dicquemare, 
Suriray, Macartney, and Baird; while in more recent times 
Verhaege, De Quatrefages, and Giglioli have specially studied 
the phosphorescence of the sea caused by Woctzluca. The light 
given out by this form is occasionally spread over a large area, 
and is often evident along the margin of the beach, where the 
broad belts of Noctilucze gleam in the broken water. It is 
not uncommon in summer on the southern shores of Britain, 
while it is rare in the northern ; but it stretches into most of 
the great oceans, and is the cause of that diffused and silvery 
phosphorescence so well known to voyagers in the warmer seas. 
At Ostend, Verhaege found the maximum number in a given 
quantity of water in the warm months, few or none appearing 
in the winter. The observations of De Quatrefages (‘‘ Observa- 
tions sur les Noctiluques,” dx. des Sc. Nat., 3° Série, Zool., 
tom. xiv. p. 226) were made on the shores of France as well 
as those of Sicily, for he accompanied the distinguished Prof. 
Henri Milne-Edwards (whose loss science has had so recently to 
deplore), on his celebrated ‘‘ Voyage en Sicile,” and they were 
more extensive than those of the previous author. He attributes 
the emission of the clear bluish light in quiet water, or the white 
light with greenish or bluish touches in broken water, to any 
physical agent which produces contraction, the scintillations 
arising from the rupture and rapid contraction of the proto- 
plasmic filaments in the interior. Thus, like Verhaege and 
others, he found no special luminous organ. Moreover, Ehren- 
berg and De Quatrefages observed that the light emitted by 
Noctiluca, though apparently uniform under a lens, was broken 
up into a number of minute scintillations when highly magnified. 
Mr. Sorby, in examining the light of this form, has been 
unable to obtain satisfactory spectroscopic results, apparently 
from its feebleness. 
Besides Wocti/uca, which was chiefly met with in inshore water, 
Mr. Murray, of the Challenger, describes various species of Pyvo- 
eystis (Proc. Roy. So-., vol. xxiv., p. 553, pl. xxi. ; and Narrative, 
Zool., vols. i. and ii., pp. 935-38), a closely-allied form, and 
indeed some of which have been thought to be identical with the 
former. They abound in the open sea, and are the chief causes 
of its phosphorescence in the tropical and subtropical oceans. 
The light is stated to proceed from the nucleus, and in this 
respect diverges from that observed by De Quatrefages in 
Noctiluca, When shaken in a glass they give out, Sir Wyville 
Thomson observes (‘‘ Atlantic,” vol. ii. p. 87), the uniform soft 
light of an illuminated ground-glass globe. 
Dr. Giglioli, during the voyage of the Italian frigate Magenta, 
mentions (Att della R. Accad. delle Sc. di Torino, vol. v., 1869- 
79, p. 492) that another group of the Protozoa, viz. the Radio- 
laria, show phosphorescent properties. In the Pacific the genera 
Thalassicolla, Collozoum, and Spherozounm shone with an inter- 
mittent greenish light. It is possible that Dr. Baird (Loudon’s 
Mug. Nat. Hist., vol. iii. p. 312, Fig. 81, c,d), in his earlier 
paper, refers to the same group when describing an unknown 
phosphorescent pelagic organism. 
No group of marine animals is more prominent in regard to 
phosphorescence than the Czelenterates. The Hydroida are 
familiar examples (even after many days and in impure water 
some of these retain this property, a shock to the stem sending 
off a crowd of luminous points from the trophosome), and, as 
Mr. Hincks observes, none excels the common Olelia geniculata, 
which forms pigmy forests on the broad blades of Laminarize 
all around our shores. In the fresh specimen a touch during 
summer causes a large number of luminous points to appear on 
the zoophytes, the stems most irritated emitting beautiful flashes, 
which glitter like faintly-dotted lines of fire, the points not being 
harshly separated, but blending into each other, while the shock 
imparted by the instrument detaches the minute medusoids, 
which scintillate upward from the parent stem to the summit of 
the water. Mere blowing on the surface in July, where Lamin- 
arize abound, suffices to produce the emission of light from the 
pelagic buds. Moreover, these minute bodies, along with the 
various species of Ceratium and minute larval forms of diverse 
kinds, are sometimes swept by the gales landward, and cause 
phosphorescence where least expected. In the same manner 
Vaughan Thompson (‘‘ Zoological Researches,” vol. i. part i. 
mem. iii. p. 48, 1829) found luminous patches on the masts and 
windward yardarms on board ship, and they gradually mounted 
upward as the gale increased. Many of the free gonosomes of 
the Hydroids are as luminous as the polypites, and indeed have 
been described by some of the older naturalists as one of the. 
main causes of the luminosity of the ocean, The light in these 
(e.g. Thaumantias) gleams around the margin and along the 
four radii. 
The Ascraspedote Medusz have also been signalised as factors 
in producing the phosphorescence of the sea, such forms as Pe/agia 
noctiluca and Pelagia cyanella being especially prominent. Spall- 
anzani, indeed, made an elaborate series of experiments on the 
luminosity of the Medusz in his voyage to the Two Sicilies. Some 
of these, as Dactylometra (Pelagia) quinquecirra, Agass., are noc- 
turnal in their habits. They are only occasionally found floating at 
the surface during the day, while at night, in the same localities, 
the bottom swarms with these large masses of dull phosphor- 
escence, moving about with the greatest rapidity (Agassiz, 
‘North American Acalephe,” p. 49, Cambridge, 1865). Spe- 
cies of Rhizostoma were likewise observed by Giglioli to have a 
pale bluish luminosity. The two most abundant Meduse of our 
eastern shores, viz. Aurelia aurita and Cyanea capillata (both 
in its young purple and adult brown condition), so far as I can 
make out, exhibit no luminosity. This agrees with the views 
expressed long ago by Ehrenberg. 
The oceanic Hydrozoa (Siphonophora) are likewise characterised 
by their phosphorescence. Thus Giglioli met with luminosity in 
Abyla, Diphyes, Eudoxia, Praya and Aglaismoides. Dr. Bennett 
(**Gatherings of a Naturalist,” p. 69, 1860) has also observed 
luminosity amongst the Coralligenous Actinozoa, the grazing of a 
boat on a coral reef causing a vivid stream of phosphoric light. 
Similar observations were made on Madrepores by Giglioli (Az 
della R. Accad. d. Sc. di Torino, vol. v. p. 502), the light in this 
case being bright greenish and enduring some minutes. 
Amongst the Alcyonarians the luminosity of the common Sea- 
Pen (Pennatula phosphorea) has been long known, and was studied 
by Gesner, Bartholin, Adler, and others. In the earlier part of this 
century Grant made the well-known and oft-quoted description 
(Brewster's Edin. Fourn. vol. vii. p. 330, 1827), in which he pic- 
tures a Pennatula “with all its delicate transparent polypi expanded 
and emitting their usual brilliant phosphorescent light, sailing 
through the still and dark abysses by the regular and synchronous 
pulsations of the minute fringed arms of the whole polypi.” But 
it ought to be balanced by his concluding statement, that the sea- 
pens are probably stationary, or ‘‘lie at the bottom, and move 
languidly like Spatangi, Asterize or Actiniz” (certainly the 
specimens in the St. Andrew’s Marine Laboratory were very 
helpless). Edward Forbes again observed that the light proceeded 
from the irritated point to the extremity of the polypiferous 
portion, and never in the opposite direction, As Dr. George 
Johnston tells us, Forbes induced Dr. George Wilson to test, 
along with Professor Swan, the polyps during phosphorescence 
by a delicate galvanometer, but without result. He thought the 
luminosity was due to a spontaneously inflammable substance. 
More recently a series of interesting observations were made 
by Panceri on the structure and physiology of the luminous 
organs of this form. His conclusions are (1) that the light 
emanates from the polyps and zoids ; (2) that the phosphorescent 
organs are the eight white cords adhering to the outer surface of 
