GEMMATION OF EADIATA AND ABTICULATA. 



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 , -ie 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 Eadiata, 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. 297. POLYPES OP 



ASTRJEA, 



Undergoing fission ; a, b, c, 

 d, successive stages. 



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 



