$74 Mr. Macartney's Observations 
body, and communicated with four or five intestinal sacs. 
The pencil drawings he made on the spot, are in the 
possession of Sir Joseph Banks, by whose permission, 
engravings from them are subjoined to this paper. By com- 
paring these with the representations of the medusa scin- 
tiilans, and some of this species rendered visible, by being a 
long time preserved in spirits, which 1 have laid before this 
learned Society, it will be found, that the only difference 
between Forster’s animalcule, and the medusa scintillans, is 
in the appearance of the opaque parts, shewn in the micro- 
scopic views. 
Many writers have ascribed the light of the sea to other 
causes than luminous animals. Martin supposed it to be 
occasioned by putrefaction : Silberschlag believed it to be 
phosphoric: Professor J. Mayer conjectured, that the surface 
of the sea imbibed light, which it afterwards discharged. 
Bajon and Gen til thought the light of the sea was electric, 
because it was excited by friction. Forster conceived that it 
was sometimes electric, sometimes caused from putrefaction, 
and at others by the presence of living animals. Fougeroux 
de Bondaroy believed that it came sometimes from electric 
fires, but more frequently from the putrefaction of marine 
animals and plants. 
I shall not trespass on the time of the Society, to refute the 
above speculations ; their authors have left them unsupported 
by either arguments or experiments, and they are inconsistent 
with all ascertained facts upon this subject. 
The remarkable property of emittinglight during life, is only 
met with amongst animals of the four last classes of modern 
naturalists, viz. mollusca, insects, worms, and zoophytes. 
