THE FIRST DIVERS 25 



One group, rather appropriately named Desis, lives be- 

 tween low and high water mark along shore, and when 

 the first drops of the incoming tide splash them, they re- 

 treat to some tiny coral cave or crevice, and weave a 

 tight silken door across the entrance. The water comes 

 higher and higher, covers the partition and buries it deep. 

 A few hours later, when the moon beckons, the waters 

 sink and as the air again reaches the cave mouth the bulk- 

 head tapestry is torn away and the spider comes forth on 

 whatever 'tween tide business of life most interests these 

 little Desis. 



This is a decided advance on the bubble-clutching 

 beetle and the rat-tailed maggot, for here we have the 

 instinct and the ability to make a dry, water-tight cham- 

 ber out of an open crevice, to fashion a temporary breath- 

 ing home beneath the waves, not by mechanical adapta- 

 tion of its body, but by the manufacture of extraneous 

 substances which, in their manipulation and use, are per- 

 fectly analogous to the paraphernalia of a human diver. 



It is left to another spider to snatch from human, sub- 

 marine inventions the last shred of originality. This is 

 known, rather unimaginatively, as the water spider and 

 for a land-fashioned air-breather it probably spends more 

 time under water than any other creature. Even when 

 newly hatched it can surround its body with a film of air, 

 and can dive and swim, usually upside down, for long 

 periods of time without renewal. 



When some instinct impels it to begin the serious busi- 



