ORDER POLYPI GELATINOSI. 497 
Hypra, Linn. 
Present us the animals of this class reduced to their greatest 
possible simplicity. A small gelatinous trumpet-shaped body, 
whose edges are furnished with filaments, which serve as ten- 
tacula, constitutes their whole apparent organization. The 
microscope enables us to discover nothing in their substance 
but a transparent parenchyma, filled with grains, a little more 
opake. Nevertheless, they swim, they crawl, they even 
walk, by fixing alternately their two extremities, like the 
leeches, or geometrical caterpillars. ‘They agitate their ten- 
tacula, and make use of them to seize their prey, which is 
visibly digested in the cavity of their body. They are sen- 
sible to light and seek after it. But the most marvellous pro- 
perty is that of constantly and indefinitely reproducing the 
parts which are taken from them, so that the individuals may 
be multiplied at will, by section. Their natural multiplication 
takes place by the young shooting forth from different parts of 
the body of the adult, and at first resembling branches of it. 
Our dormant waters nourish five or six different species of 
them, which differ in colour, and the number and proportion 
of the tentacula. 
The most celebrated, in consequence of the experiments on 
reproduction, to which it has first given occasion, is 
Hydra viridis, Trembley, Pol. i. 1. Rees. iii. Ixxxviii. 
Encyc. Ix. vi., which is, in fact, of a fine clear green colour. 
It is particularly found under the water-lentils. 
Hydra fusca, 'Tremb. Pol. i. 3, 4. Rees. iii. Ixxxiv. Encyc. 
]xix., is more rare ; of a grey colour; its body is not an inch 
long, and its arms are more than ten. 
CORINE, Geriner, 
Have a fixed stem, terminated by an oval body, more con- 
sistent than that of the hydre, open at the summit, and brist- 
VOL. XII. K k 
