224 FLASHLIGHTS ON NATURE 



awaking refreshed in April, come to the surface once 

 more, where they begin their gyratory antics all over 

 again, da capo. It is a merry life ; and though 

 the whirligig can fly, which he does occasionally, 

 'tis no wonder he prefers his skimming existence 

 on the still glassy sheet of his native waters. 



The two larger British water-beetles, which are 

 such favourite objects in the aquariums of young 

 naturalists, do not lead quite so exclusively aquatic 

 a life ; they pass their youth as larvae in the pond, 

 and they return to it in their full-winged or beetle 

 stage, being most expert divers ; but they both 

 retire to dry land to undergo their metamorphosis 

 into a chrysalis, and they spend their time in the 

 pupa-case in a hollow in the ground. Something 

 similar occurs with many other aquatic animals, 

 which are thus conjectured to be the descendants 

 of terrestrial ancestors, whom the struggle for life 

 has forced to embrace the easier opening afforded 

 by the waters. 



In this respect, that rather rare and beautiful 

 little water-plant, the frogbit, shown in No. 9, 

 has a life-history not unlike the career of the 

 water-beetles. It is a quaint and pretty herb, 

 which never roots itself in the mud, like the curled 

 pond-weed, but floats freely about on the surface, 

 allowing its long roots to hang down like streamers 

 into the water beneath it. The short stem or stock 

 is submerged ; the leaves expand themselves freely 

 and loll on the surface. Like most other floating 

 water-leaves which thus support themselves on the 

 top of the water, they are almost circular in form 



