Let these test tubes standin good light,butnotindirectlight, for several
days.
You will observe: The lone snail in the first test tube will die as will the
plantin the thirdtest tube. Eventhoughit is sealed, andthereforeclosed off
fromthe oxygen in the air, the second test tube hasprovidedconditionswhich
sustainlife. Both the snail and theplantare alive andperhapseven thriving.
The plant supplies the snail with food andoxygen. In turn,the snail
provides the plant with minerals and carbon dioxide. The light provides
enoughenergy for the plantto puttogetherthe carbondioxide, waterand
certainmineralsto manufacturefood for itself and for the snail. Now you
can see why it is soimportantto include greenplantsinyouraquarium.OBSERVING THE METAMORPHOSIS OF AFROG
Materials: Collect frog eggs from the shallow water of apond earlyin
the spring. Putthem inyouraquariumor in a largejarofwatercontaining
a fewpondweeds.
Follow thisprocedure:Keep the little black andwhite eggsthatare sur-
roundedby a mass of gelatin in the samewateruntil they develop. Seethat
they getsunshineor light from an electric bulbduringthedaytimehours.
Afterthe fish-likeyoungtadpolesdevelopfromthe eggs, feed them bits
ofboiledlettuceleafeachmorning. Be sure to remove the uneatenfood at
the end of the day sothatthetadpoleswill not be killed by the decayproducts
oftheleftoverlettuce.
You will observe:The mass of eggs issurroundedby atransparentgelatin
substancethatkeeps it floating near the surface of thewater. Theprotective
gelatinalso acts as amagnifyinglens, for itconcentratesthewarmrays of the
sun on eachdevelopingegg.
Aftera periodofabout8 to 20 days,dependingon theamountofsunshine
orheatthe eggs get, fish-likebabyfrogs, ortadpoles,will wiggleoutof the
eggsandgelatin mass. Tadpolesswim like fish.
After about9 days, each tadpolewill develop hind legs. Then,as the
tadpolescontinueto grow, their tails will become increasingly shorterand
frontlegs willappear. Duringthis time thetadpoles'bodies will begin tolook
more frog-like.
Finallyeachtadpolewill become anadultfrog with twopairsof legs and
no tail. Each will try to leave thewaterinsearchofa rock on which to sit.
Becareful! They mayjumpright outofyouraquarium! Nowit'sbest to
takeyourfrogs to the woods and let them freeneara pond.