282 



ELEMENTARY BIOLOGY 





6 <f 



Fish, Chinook salmon {Oncor/iji/icAus tscha^vytscha) 



a 



■'■ P •9 



) .5:' . " '**?*. 5?^ 



3^i 





Batrachian, frog {Rana palnstris) 



Batrachian, newt {A inblystovia pjtndatiivi) 



Fig. ii8. Development in some backboned animals 



a, egg: a^. fish ready to break out of egg: b, first free-swimming stage (tadpole in 

 batrachians) : (''j. later stage in fish, still showing yolk sac: c. more advanced stage (in 

 batrachians, tadpole just before the appearance of hind legs) : d, later stage ; e, adult form 



during the three weeks of hatching something was going on 

 inside the eggshell of the chick. 



The development of an individual through a series of 

 well-marked stages is called a metamorphosis, w^hich means 

 " trans-formation." 



