DEVELOPMENT PRIOR TO LAYING 30 
grating wall (Fig. 9). The chromosomes and nucleoli form a 
group near the center of the upper plane surface of the germinal 
Fig. 9. — Vertical section of the germinal vesicle and part of the germinal 
disc of an ovarian ovum ? inch in diameter; pigeon. x 385. (After 
Harper.) 
Chr., Chromosomes. Gr., Granulosa. G. V., Wall of germinal vesicle. 
? bf 5 
vesicle. The first maturation spindle is formed before ovulation, 
containing eight quadruple chromosomes (tetrads). The spindle 
is still in the equatorial plate 
stage when the ovum is 2 OS Se 
grasped by the mouth of the | is Ys N ok, 
oviduct (Fig. 10). The bulk | S/, Tit 2 7 Spl 
of the substance of the ger- | o Os abe 
minal vesicle soon forms a NE Was 
yolk-free cone extending | on BRK 
from the maturation spin- , Pes aN 
dle deep into the superficial, _ 4 
yolk. The outer end of the Fria. 10.— Vertical section of the germinal 
spindle is in almost imme- dise of the pigeon’s egg showing the 
F . irs aturation spi . The egg was 
diate contact with the sur- first maturation spindle le egg was 
clasped by the funnel of the oviduct. 
face of the ovum. In the : . 
: : 8.50 p.M. x 2000. (After Harper.) 
later stages of formation of m. Sp. 1, First maturation spindle. Tetr., 
the first polar body each Tetrad. 
tetrad, or quadruple chromosome, separates into two dyads or 
double chromosomes, and the members of each pair of dyads 
separate and approach opposite ends of the spindle (anaphase). 
