ON POLYPI. 5TP 
or not. These animals, moreover, can support a very long 
fast, probably, because they absorb directly from the medium 
in which they live. 
The reproduction of the hydrez is still more simple, if 
it be certain that it takes place by buds in all parts of the 
external surface of the body. During the summer, it is said, 
that a little germ is observed to project from some part of this 
surface, which enlarges by degrees, and assumes the figure of 
the mother. Very soon from its free extremity we see like- 
wise the tentacula sprout forth ; and at the end of a longer or 
shorter time, which depends a little on circumstances, more 
or less favourable, the young hydra, which, while it was at- 
tached to the mother, sought and attracted its prey like her, 
and fed upon it, ends by being detached from her, and pro- 
ceeds to fix itself upon some submerged body, where it re- 
produces in its turn in the same manner. Sometimes it 
even reproduces while attached to the mother ; insomuch that 
even eighteen of these animals have been reckoned thus 
united. 
The reproductive faculty of the hydre, carried to the 
extent observed by Trembley, must tend to make us be- 
lieve that this power is extended to all parts of the body. 
In fact, after the very delicate experiments, but authen- 
ticated beyond all doubt, of a philosopher so entirely wor- 
thy of credit as Trembley, it is evident that not only the 
various parts of the body, cut longitudinally or transversely, 
can reproduce the parts that are deficient, and thus form so 
many complete animals, often in two days only; but even 
sometimes a portion of tentaculum can be developed, and 
produce a perfect hydra, which Roésel assures us that he has 
observed. 
But it is not only by gemmation, or by artificial or sponta- 
neous scissure, that the hydrz can be reproduced. Jussieu, 
Trembley, Roésel, and Pallas himself, have observed, that 
VOL. XII. Pp 
