Luminousness of the Sea. 3a 
were of as much use seriously to refute it, as to sit down and 
cavil with the opinion of the poet who describes the luminous 
nature of the sea to be 
“ As though the lightnings there had spent their shafts, 
And left the fragments glittering on the field.” 
It is equally unprofitable to take notice of the other 
theories, they are all vague and unsatisfactory, they are all 
unsupported by facts; while the true cause, the existence of 
animalcules, receives support t and confirmation by every day’s 
experience, and rests upon facts, numerous and easily prov ed. 
Suffice it at present to say, that the animalcules have been 
caught in the very act of giving out the luminous appearance, 
and in vast numbers ; and that, in every instance where the 
water has been properly examined when luminous, great 
quantities of animalcules have been seen; and that, on the 
contrary, when the water has not been luminous, the animal- 
cules have not been present, thus affording satisfactory proof 
that they are the cause of the light so given out. 
I have already said that a considerable variety of marine 
animals have been described and figured by authors as lumi- 
nous. Amongst the Molldsca, the Pholas dactylus has long 
been known is possess this property, having been described 
as luminous by a naturalist well known in this Society, I mean 
Pliny. Amongst the Vérmes, the Néreis noctiluca is also well 
known. Amongst the Crustacea, several species of the genera, 
5 
Cancer, Lyncéus, and Limulus ; and, amongst the zoophytes, 
several species of the genera Medisa, Béroe, and Pennatula 
have long ago been described as possessing the same property, 
while an immense number of new genera and species have 
been ascertained by Dr. Macculloch, but which have never 
yet been published. It is with the intention, therefore, merely 
of adding my mite to the information already acquired upon 
this subject, and attempting to extend our knowledge with 
regard to the species of animalcules which inhabit the sea and 
possess a luminous quality, that I presume to offer the follow- 
ing descriptions and remarks. 
In an excellent paper by Mr. Macartney, in the Phil. Trans. 
1810, that gentleman describes and gives representations of a 
considerable number of these ; and, from various observations 
and patient research, he concludes that on our coasts, and per- 
haps in general throughout the ocean, the luminousness of the 
sea depends chiefly upon one species, which he denominates the 
Medusa scintillans. During a late voyage to India and China, 
I had various opportunities of observing the animals which 
