1044 REPORT—1885. 
what he called microscopic animalcula,' apparently Infusoria, were phosphorescent; 
and fully half a century later Pfaff noticed that the luminosity of the sea at Kiel 
was due to certain members of the group just mentioned. Subsequently both 
Michaelis and Ehrenberg met with phosphorescent Infusoria in the Baltic, the 
latter describing them as species of Peridintwm (now Ceratium), and Prorocentrum. 
The same fact, associated with the absence of Nocttluca at Kiel, has again more 
recently been brought forward by Stein. In our own seas I have been especially 
struck with this feature in July and August, the whole surface of the sea along 
the eastern shores of England and Scotland teeming with Ceratiwm and 
Peridinium, besides other Infusoria, which form a greenish scum on the interior of 
tow-nets in inshore water, and for many miles seaward. As the waves curl from 
the sides of the boat in quiet water, the crest of each sparkles with multitudes of 
luminous points, which gleam for a 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 a few seconds and then fades. I have been 
unable, nevertheless, to satisfy myself as to the phosphorescence of isolated examples 
of Ceratium, and Mr. Murray (who is inclined to follow Klebs in considering 
them Alez) tells me that he has not been more successful. 
The most conspicuous member of the first group (viz., the Protozoa), how- 
ever, is Noctiluca, 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 3 to 4 ofa millimétre, 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 
nayal surgeon, who examined it off various parts of the French coast 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.” 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 Noctiduca. 
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 Noctiluce 
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® were made on the shores of 
France as well as those of Sicily, for he accompanied the distinguished Professor 
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 protoplasmic filaments in the interior. Thus, 
like Verhaege and others, he found no special luminous organ. Moreover, Khren- 
berg and De Quatrefages observed that the light emitted by Noctiluca, though 
apparently uniform under alens, was broken up into a number of minute scintilla- 
tions when highly magnified. _Mr. Sorby, in examining the light of this form, 
1 Opuscula Subseciva, vol. i. p. 31. tab. iv. fig. 1. 
2 Journal des Savants, tom. xiii. Feb. 1770, pp. 554-561. 
8 «Observations sur les Noctiluques,’ Ann. des sc. nat. 3° Série, Zool., tom. xiv. 
p. 226. 
