THE GERM-CELL CYCLE 
IN ANIMALS 
BY 
ROBERT W. HEGNER, Pu.D. 
ASSISTANT PROFESSOR OF ZOOLOGY IN THE UNIVERSITY 
OF MICHIGAN 
AUTHOR OF “AN INTRODUCTION TO ZOOLOGY” 
AND “COLLEGE ZOOLOGY” 
New Bork 
THE MACMILLAN COMPANY 
1914 
All rights reserved 
