CHAPTER XIV. 



THE STUDY OF FRESH-WATER ANIMALS. 



IT will be best in dealing with this subject here to 

 confine our attention to the animals likely to find a place 

 in a small fresh- water aquarium or school collection. 



And first it seems desirable that in the teacher's mind 

 at all events the mixed company of the aquarium inmates 

 should be reduced to order. To facilitate this the follow- 

 ing facts of classification are submitted. 



CLASSIFICATION. 



AMPHIBIA. Newts, Frogs, Tadpoles belong to Class 

 Amphibia. Cold-blooded Vertebrate animals, naked skin- 

 ned, breathing by gills in young state (i.e. aquatic), 

 possessing lungs as adults (i.e. with power of terrestrial 

 respiration). Limbs have clawless fingers and toes. 



PISCES. Sticklebacks, Minnows, Carp, etc. Class 

 Pisces (Fishes). Cold-blooded Vertebrate animals, scaly, 

 breathing by gills ; limbs are fins. 



MOLLTJSCA. Pond Snails, e.g. Lymnaea, Planorbis, Ancy- 

 lus (lung breathing) ; Paludina (gill breathing), Uni- 

 valves of Class Mollusca. Soft-bodied Invertebrates, 

 without appendages, with mantle and foot; limy shells. 



180 



