178 THE HAUNTS OF LIFE 



be able to remain under water for consider- 

 able periods, because they have various ways 

 of carrying reserves of air, as bubbles en- 

 tangled among the body-hairs, for instance, 

 while others are able to use the oxygen mixed 

 with the water. 



In addition to these, many insects, such as 

 the gnats, may-flies, caddis-flies, and the beau- 

 tiful big dragon-flies, lay their eggs in the 

 water, and the great changes from egg to 

 larva, from larva to the " resting-stage," which 

 is a preparation for the emergence of the per- 

 fect insect, are gone through in the water. 

 Yet this is not a case in which an aquatic race 

 is on the way to terrestrial life; they are not 

 water-breathers, they are air-breathers, which 

 have adopted the habit of laying their eggs 

 in the water for the greater safety of the 

 young. Many of the larvae have become so 

 well adapted to aquatic life that they are able 

 to breathe dissolved air by gills, but these 

 "tracheal gills," as they are called, are de- 

 veloped from the air-tubes which are present, 

 even though the openings to them are closed. 

 And many of the larvae breathe surface air 

 from the first. The gnat larvae, which we may 

 find in any ditch, have a breathing-tube pro- 



