GEMMATION OF RADIATA AND ARTICULATA. 555 
are in reality the representatives of the flower-buds of Plants, 
distinguished by their capability, not only of living and en¬ 
during, but of obtaining their own nu¬ 
triment, after their spontaneous detach¬ 
ment from the stock that bore them. 
Among the Medusae we occasionally 
meet with instances of propagation 
by buds that resemble the stock from 
which they proceed, and that are 
thrown off in due time so as to lead 
independent lives; but this kind of 
gemmation seems limited to the lower 
members of the group. In a large 
proportion of it, however, a very extra¬ 
ordinary kind of multiplication by 
gemmation takes place at an early 
period of development (§ 740).—In 
the highest Radiata, the class of 
Echinodermata , we take leave of multiplication by gemmation 
altogether; for although the* bodies of these creatures possess 
a very extraordinary reproductive power, so that the result of 
very severe injuries may be repaired (§ 389), we do not find 
that they either spontaneously produce independent buds, or 
that they have the capacity for being multiplied by artificial 
division. 
727. Among several of the lower Articulata, detached 
segments of the body appear to be capable of reproducing the 
whole; and there are some whose ordinary propagation is 
Fig. 298.— Nereis Prolifera. 
accomplished by an exercise of this power. Thus in the Nais, 
an aquatic worm allied to the Earth-worm, the last joint of the 
body gradually extends and increases to the size of the rest of 
the animal; and a separation is made by a narrowing of the 
Fig. 297.— Polypes of 
Astr^ea, 
Undergoing fission; a , b, c, 
d, successive stages. 
