THE "SWIMMING-BELL." 17 



Two methods of dispersal. When 

 these reproductive buds reach a certain stage 

 of maturity, it will be found that two different 

 methods of dispersal are adopted. 



"Reproductive" buds either fixed 

 or free. In one case, the buds (of either sex) 

 become detached and migrate, fertilization 

 taking place either before or after. In the 

 other they remain attached. The ova are set 

 free on the spot and disperse, and are termed 

 "planulse." 



"Swimming-bell." In the first case 

 (mainly obtaining amongst the lower forms), 

 the young bud is liberated ; it then assumes 

 the condition known as the swimming-bell, 

 and propels itself through the water by means 

 of cilia, to which reference is made hereafter. 

 The bud itself is essentially a polypite, that is 

 to say, it possesses a typical mouth and 

 stomach. 



Development of the "bell." The 

 animal in the region of the tentacles becomes 

 greatly expanded laterally at the expense of 

 that portion of the body below the tentacles, 

 and now takes a cup or saucer-like form, 

 overhanging the free, oval end of the animal. 



