lo THE PHYSIOLOGY OF TWINNING 



Throughout the book an attempt is made to put the 

 various types of twinning in their proper place in the 

 system of biological phenomena and to show in what 

 ways a knowledge of the causes and consequences of 

 twinning helps to advance our knowledge of several 

 obscure and difhcult but none the less fundamental 

 aspects of animal biology. 



