ON ACALEPHA. 563 
they are also united in a more or less considerable portion of 
their extent. From this results a pedicle, sometimes very 
thick, which appears to divide the mouth into four parts. 
These acalephe, which vary considerably in bulk, since, 
though there are some truly microscopic, there are others 
which attain to several feet in diameter, and weigh fifty 
pounds, are of ail animals those which have the least of solid 
substance. They are composed, as it were, of a sort of jelly, 
more or less consistent, perfectly transparent, which, in con- 
sequence of the loss of life, resolves itself into a limpid salt 
water, leaving as aresidue but some grains of membranaceous 
parts equally transparent. , 
The tissue of the meduse is not then really homogenous, 
though it appears to be so. Their skin, or envelope, is never- 
theless of an extraordinary thinness, not distinct. This may 
be considered but as the boundary of their tissue a little con- 
densed. Observed with a microscope, M. Gaéde perceived 
that it was furnished with small grains, each of which ap- 
peared to be composed of grains still smaller. Might this be 
the source of the viscous matter, which transudes from all 
parts of the body, and which Peron says that he has ob- 
served in individuals put into sea-water frequently renewed, 
to enable them to preserve all their vital activity, and which 
is so abundant, that the thirtieth portion of water is as much 
charged as the first. This does not seem probable. It 
might, perhaps, rather be believed that this is the origin of 
the eminently phosphorescent substance, which Spallanzani 
has remarked in certain parts of the body of the luminous 
medusz, and which possesses properties different from those 
of the liquor which issues from a wound. ‘The latter has the 
taste of salt water, and the other causes a painful sensation, to 
that degree that having touched it with his tongue, Spallan- 
zani felt a burning impression which lasted more than a day ; 
a drop having by chance fallen upon his eye, the pain was 
002 
