THE EGG 31 



known if maturation in birds may be completed without fertiliza- 

 tion, but it seems probable that, as in many other animals, the 

 completion of maturation is dependent on the stimulus of fertihza- 

 tion. It is, however, essentially a process absolutely distinct 

 from fertilization, and in some animals {e.g., echinids) is com- 

 pleted without fertilization. 



