578 SUPPLEMENT 
towards autumn, they eject from their parenchyma some eggs, 
which fall, are preserved during the winter, and are not deve- 
loped until spring. It is also said, that the individuals which 
have their origin in this mode of reproduction, are always 
smaller than those which have come by gemmation. It has 
been questioned, however, whether these are in reality eggs. 
Thus the history of the hydra, in considering it as well 
authenticated, brings to general physiology some considera- 
tions of the greatest importance, since it exhibits to us an 
organized body, composed of a homogeneous tissue, conse- 
quently without distinction or separation of organs, not even 
of skin and muscular fibres, endowed with a very great sensi- 
bility, which permits it to feel the light, extremely contractile 
in all its parts, which can seize small animals of greater re- 
sisting solidity than itself, introduce them into its stomach, 
and digest them ; and that not only with the surface which is 
5 
habitually digestive, but also with the external surface, arti-— 
ficially become internal. It displays to us an animal, that 
can graft itself upon another, or by a true continuity of sub- 
stance, can form, by the union of several individuals, a com- 
plex animal, with many heads, thus realizing in nature, the 
hydra of the fable; considerations which would lead us to 
believe that the hydrze are very inferior to the polypi of the 
madrepores, and to those of the pennatule, &c. which are 
evidently much more complicated in their organization, and 
that consequently they ought to form the last link of the chain 
of radiated animals. 
Hydre are to be found in all fresh waters, and in those of 
the sea, but more particularly, as it would appear, in the first, 
when they are dormant, providing that be pure. It is during 
summer that we must look for them, on all bodies submerged 
in such waters; for, during winter, it seems that they contract 
themselves and sink into the mud. They may be easily pro- 
cured by taking acertain quantity of water-lentils, and putting 
ae ~~ 
