THE GERM-CELL CYCLK 

 IN ANIMALS 



BY 



ROBERT W. HEGNER, Ph.D. 



ASSIST.AJNT PROFESSOR OF ZOOLOGY IN THE UNIVERSTTY 



OF IVnCHIGAN 



AUTHOR OF "an IXTRODUCTIOX TO ZOOLOGY 

 AND "college zoology" 



Neb) gorfe 



THE MACMILLAN COjMPANY 



1914 



All rights reserved 



