ON ACALEPHA. 567 
back. They are sometimes thrown in great quantity upon the 
shores of our climate, where endeavours have been made to 
turn them to some advantage. It has been attempted, but 
without much success, to extract ammonia from them. ‘They 
have been more beneficially employed in the way of manure 
upon arable land. 
All the medusz in a state of death and putrefaction, appear 
to be phosphorescent ; but there is only a small number which 
appear to be so in the living state. We are indebted to 
Spallanzani for a great number of curious experiments on 
this subject. He first endeavoured to discover what the parts 
are which more particularly possess this singular property. 
And he found that they were, Ist. the great tentacula, or arms. 
2nd. the muscular zone of the umbrella; and 3rd. the stoma- 
chal cavity. The rest of the umbrella only shines by trans- 
mitted light. He then occupied himself in observing to what 
cause the phosphorescence is owing, and he became convinced 
that it was to a peculiar glutinous humour, which issues from 
the surface of the three parts just mentioned. This, however, 
as we have said farther back, is altogether different from that 
which issues from the body, and even from these same parts, 
when they are cut. It is very corrosive, and its application 
on the hand, and on the tongue more especially, occasions a 
lively sensation of pain. Expressed into different liquids, as 
into salt water, but particularly into fresh water warm, or 
milk, it communicates to them a phosphoric light. A single 
medusa thus expressed into twenty-seven ounces of cow’s 
milk, rendered it so resplendent, that one might have read the 
characters of a letter by it, at the distance of three feet. At 
the end of eleven hours, it retained some degree of light ; when 
it had lost this altogether, it was renewed by stirring it, and, 
finally, when this means no longer produced any effect, it 
was again obtained by heat, care being taken that the heat 
was not too strong. The dead medusa also still possessed 
