i 
378 Some Account of the Meduse 
tive system of the equorer, itseems to be of considerable 
energy; for, independently of the rapid growth and of the 
Jarge dimensious which these animals may attain, there is 
a pecuharity in their history which supposes a force of. re- 
paration and of assimilation very powerful, 
Exeretions —If we put one of these zoophytes into a 
vessel filled with several litres of pure sea-water, the trans- 
parency of the liquid is soon disturbed; glarey flakes be- 
eome visible in all parts of the water; they increase so ra- 
pidly, that in avery short time we sce the animal expire 
in the midst of the excretions which he has furnished. If 
we take care frequently to renew the water of the vessel, 
the medusa will preserve all its activity ; but so great at all 
times is the abundance of the viscous matter which tran- 
sudes from all parts of its body, that the twentieth portion 
of water will be altered by it as speedily as the first. What 
can be the excretory ducts of so extraordinary a kind of 
transpiration? We have not been able to discover any 
thing satisfactory on this-head; and the solution of the 
problem is the more difficult, because the substance of the 
umbrella seems to be more completely foreign to vascular 
organization, thau such an excretion would seem to re- 
quire. 
Contractibility.—In treating of the locomotion of the 
equoree, we have only said a single word of the force of 
contraction which essentially characterizes all the animals 
of the great family of the meduse: we shall on a future 
oceasion revert to the subject of the principal scat and the 
agents of this valuable faculty: it is under a point of view 
completely novel that we are about to consider it in the 
following account of our investigations, and of the dis- 
covery which we think we have made in this respect. 
Respiration —Tbe contractibility in question is mani- 
fested by a phanomcnon so striking, that it is not astonish- 
ing that most writers have made particular mention of it. 
All are agreed im assigning a peculiar system of locomo- 
tion and progression to the alternare contractions and di- 
Jatations of ibese zoophytes. This assertion is doubtless 
correct, and the deiails which we have ourselves given on 
this subject cannot Jeave any reasonable doubt as to this es- 
senual point of the history of the medusz. But are these mo- 
tions, so constant and so regular, exclusively dedicated to 
this last function? Thisis the problem which we shall try 
to resolve, 
lf we observe any medusa cn. the surface of the sea, 
and under any given circumstances, we sec it alternately 
contract 
