ORDER POLYPI POLYPIFERI. 499 
LHIRD ORDER OF POLY Pi. 
POLYPIFEROUS POLYPI 
Form this numerous series of species, which for a long time 
were regarded as marine plants, and whose individuals are, in 
fact, united in great numbers, to form composite animals, for 
the most part fixed like vegetables, whether they form a stem 
or simple expansions, by means of the solid supports which 
line them at the interior. The individual animals, more or 
less analogous to the actiniz, or hydre, are all connected to- 
gether by a common body, and receive their nutriment in 
common ; so that what is eaten by one, profits the general 
body, and all the other polypi. They have also a community 
of volition ; at least, this is certain with respect to the species 
not fixed, such as the pennatula, which are seen to swim by 
the contractions of their stems, and by the continued move- 
ments of their polypi. 
The name of polyparia has been given to the common parts 
of these composite animals. They are always formed by depo- 
sition, and by strata, like the ivory of the teeth ; but sometimes 
they are at the surface, sometimes in the interior of the com- 
posite animal. These different positions have given rise to 
the establishment of the families of this order. 
The first family, 
POLYPI TUBIFERI, 
Inhabit tubes, the common gelatinous body of which traverses 
Kk2 
