330 SCHOOL EQUIPMENT AND ITS MANAGEMENT. 



life. Some weed, e.g. Canadian pond weed, water starwort, 

 should be growing in the vessel. 



In their later stages tadpoles may be given very small 

 particles of meat, bread or fish, but great care must be 

 taken that such is not left to rot and pollute the contents 

 of the vessel. Have some fresh- water shrimps (Gammarus) 

 present. After the hind limbs have appeared the tadpoles 

 will thrive better in a shallow dish which contains moss or 

 stones, enabling the tadpoles to rest with their nostrils 

 above water. When the frogs are developed, and their 

 final changes from the tadpole stage demonstrated, they 

 should be taken to the side of a ditch or pond and set at 

 liberty. This is a point of great importance, and should 

 on no account be omitted. 



Water Fleas. These can usually be found in great 

 abundance in pools on moors or marshy places. A jar 

 containing a supply of these constitutes a pleasing centre 

 of observational interest and study. For observational 

 purposes they are best kept in a flat jar of the shape shown 

 in Fig. 174 6 . Mud should be placed at the bottom, and 

 from time to time the "fleas" should be given a little 

 direct sunlight. Examine with the help of a magnifier 

 mounted on a handle. 



Gnats, Pond Skaters, Whirligig Beetles. A jar exposing 

 a large surface of water and of moderate depth is best for 

 these. A sandy bottom with weeds growing out of the 

 water around the margin is also conducive to success with 

 these and also give an attractive appearance to the vessel. 

 The surface of the water should be some distance from the 

 top of the jar. Such a vessel containing larval gnats, pond 

 skaters, whirligig beetles, pond snails, affords excellent 

 opportunities for the study of the properties of the surface 

 film of water, and of the various uses small animals make 

 of it. This jar should have a wire gauze (small mesh) or 

 muslin cover, to prevent the escape of the inmates. 



Various other common inmates of pools may be found 

 by the enthusiastic collector, such as water boatmen, water 

 scorpions, water spiders, water mites, flat worms, pond 



