CONTENTS 



Introduction P^S<^ H' 



Stages of development ^4^ 



Comparative Studies in Development 



The Brain H9 



The Feathers ^S^ 



The Cartilaginous Skeleton iS4 



The Heart ^57 



Discussion ^°° 



Summary ^"^ 



Acknowledgments i"2 



List of Literature i"3 



Plates I to VI following page 164 



