42 
of 
GERM-CELL CYCLE IN ANIMALS 
chromosomes and the amount of chromatin in 
the germ cells. Typically, both male and female 
germ cells divide twice during the process of matura- 
PRIMORDIAL 
GERM-CELL 
MULTIPLICATION 
PERIOD 
SPERMATOGONIA..--—~ 
nN 
GROWTH 
PERIOD 
PRIMARY 
SPERMATOCYTE OTT 
SECONDARY 
SPERMATOCYTES 
MATURATION 
PERIOD 
SPERMATIDS 
SPERMATOZOA 
Fic. 
MULTIPLICATION 
PRIMORDIAL 
GERM=CELL, OT 
PERIOD 
OOGONIA er 
aN 
GROWTH 
PRIMARY = PERIOD 
oocyTE 
SECONDARY 
oocyTes 
(OVARIAN EGG 77 MATURATION 
‘AND POLAR. BODY) PERIOD 
MATURE EGG 
AND 0 --=-~———=-=-- 
POLAR BODIES 
9.— Diagrams illustrating (above) the stages of spermatogenesis 
and (below) of oédgenesis. The primordial germ cell is represented 
as possessing four chromosomes. 
