io8 THE WONDER OF LIFE 



It is well known that specimens of the brine-shrimp 

 (Artemia) can often be got by keeping a solution of Tidman's 

 Sea-Salt for some days till the desiccated germs hatch out. 



Belonging to another series are the adaptations which 

 enable freshwater animals to meet the winter, which in 

 northern countries sets a spell on many forms of hfe. It 

 sends many to sleep, like the frog in the mud by the pond 

 side — ^mouth shut, nostrils shut, eyes shut, breathing by 

 its skin Uke a worm, and with its heart beating ever so 

 feebly. It sends others to the deeper sleep of death, for 

 just as winter prunes the trees, so it sifts the fauna of the 

 pond. There is severe eUmination, and it is therefore 

 very interesting to notice the ' winter-eggs ' of water-fleas 

 and Rotifers which are able to withstand great severities 

 of temperature, and the strange ' statoblasts ' or resistent 

 germs of Polyzoa, and similar adaptations for surviving 

 difficulties by a Fabian policy of waiting. A good example 

 is the freshwater sponge, which spreads exuberantly over 

 stones and submerged roots in the summer, but soon feels 

 the pinch in autumn. The body of the sponge dies away, 

 and rots away, but in the skeletal framework, which 

 cannot rot, clumps of cells are formed, buttressed round 

 by capstan-hke flinty spicules, and these gemmuks, as they 

 are called, persist as foci of hfe while the parental corpse 

 disintegrates. When the spring comes and the rivers are 

 in flood after the melting of the snow, the sponge skeleton 

 is broken and the gemmules are carried hither and thither, 

 many, perhaps most, to destruction, a few to find a harbour 

 in suitable crevices where they may proceed to develop 

 into early sunomer sponges. 



In times of severe frost many animals seek safety in the 

 mud — a refuge from being imprisoned in the ice. There 



