1 82 WONDERS OF POND LIFE. 



Their hind legs, which they move to propel their 

 boat-like bodies through the water, precisely as a 

 single rower propels a boat, are very long and made 

 broad, like oar-blades, by the thick, long hairs. 



What finely constructed row-locks ! Old as the 

 world, and never patented ! There they go. How 

 nicely they feather their oars — why, Hanlon never 

 dreamed of such a stroke. 



Here is a white leech, measuring its slow length 

 along the side of the tank. Has any naturalist 

 noticed this species ? What wonderful maternal 

 forbearance and affection ! Fourteen little young 

 leeches, all very much attached (literally) to their 

 loving mother. 



Twisted around the stem of a water-cress is the 

 Grordiuz aquaticus, or hair-worm. This specimen 

 is one foot long, and no larger than a common hair 

 of a horse's mane or tail. It is continually in 

 motion ; now tying itself into a complicated knot, 

 now straightening itself out to its full length. 

 The general belief that they are transformed horse- 

 hairs is incorrect. The history of their develop- 

 ment from the egg is most interesting. After 

 hatching, the larva escapes into the water and casts 

 about to find some neighboring aquatic fly-maggot, 

 upon which it fastens itself and finally penetrates 



