PLANT-ANIMALS, OR ZOOPHYTES. 163 



brilliant eye-spots glitter on the bulbous bases of the. 

 tentacles. To their other charms that of phospho- 

 rescence is often added ; they are not only painted 

 like the flower, but at night they are jewelled with 

 vivid points of light, set round the margin of the bell, 

 or one central lamp illumines the little crystal globe, 

 and marks out its course through the water. Though 

 individually minute, their numbers are so immense 

 that they play an important part in the production 

 of the luminosity of the ocean. The surface of the 

 sea, for miles together, is often thickly covered with 

 them ; and on still, sunny days in autumn, certain 

 species swarm in immense shoals off the coast. Like 

 miniature balloons they float suspended in the water 

 for awhile ; then they suddenly start into motion, 

 propelling themselves by a series of vigorous jerks, or 

 casts, and at the same time contracting the tentacles 

 into the smallest compass ; then they become quies- 

 cent again, and sink slowly and gracefully, like para- 

 chutes, to the bottom of the vessel, some of the arms 

 extended laterally, and the rest dependent. In all 

 cases locomotion is effected by the pulsation of the 

 swimming-bell." 1 



Increase by means of budding, which is so general 

 in the " colony," is by no means absent from the free 

 swimming polypes. It is not unusual when the true 



1 Hincks's " British Hydroid Zoophytes," p. xxx. 

 M 2 



