FISHES— AQUARIA 169 



animals. So keep the water-scorpions and electric-light 

 bugs, dragonfly larvs, perch, bass, turtles, and frogs by 

 themselves, or with those too big for them to eat, un- 

 less you wish to add the smaller animals as food for 

 them. 



Goldfish may be fed on bread and cracker crumbs, or on 

 the "fish food," which can be bought. Other fish and tad- 

 poles will also eat these things. Carnivorous fish will have 

 to be fed on insects, worms, and bits of meat. A piece of 

 beef that has the fat boiled out, dried, and crushed into 

 minute bits is an excellent fish food. I keep a large food- 

 jar containing algae and other water plants and various 

 kinds of animalcula. Occasionally I put some of these 

 plants with the animalcula that cling to them into the aquaria 

 as food. In feeding aquarium animals be careful not to give 

 them more than they will eat, else the decaying food left over 

 will make the water sour and stagnant. 



The fish should be studied as a type of animal life, with 

 special reference to its structure, breathing, swimming, 

 spawning, and other habits. 



Let the children observe the fish in the aquarium. Note 

 the flattened and tapering shape of the body. Is this shape 

 of any special use ? Why have most fishes this shape ? How 

 does the fish swim? It will be seen that the fish propels 

 itself with its tail, using it as a sculling oar, and that the fins 

 are not so much used for swimming as for balancing and 

 directing the course. With rubber bands slipped over the 

 back and side fins, try Professor Needham's experiment to 

 see how a fish behaves without the use of these, and to dis- 

 cover their proper functions. Note the sharp spines on the 

 fins (if the fish is a spiny-finned one). Ask the children 



