PROBLEM 3. Explanation of Some Puzzling Facts 



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Fig. 500 (top) Front ap- 

 petidage of ?noiikey, bat, cat, 

 and seal. What si?nilarities do 

 you note? In what region do 

 you note the greatest dif- 

 ferences? How can these 

 similarities and differences 

 be explained? (ward's nat- 

 ural SCIENCE establish- 

 ment) 



Fig. 501 (right) In what 

 ways are these early em- 

 bryos alike? By what differ- 

 ences can you tell the7fi 

 apart? 



Frog 



Turtle 



Chick 



Pig 



Man 



Fig. 502 (right) Embryos 

 in later stages. As differen- 

 tiation goes on, the embryo 

 looks more and more like 

 the adult. 



