448 WILLIAM M. GOLDSMITH 
central part of the former nuclear area and the granular cyto- 
plasm crowds in from all sides. The spindle fibers now appear 
and the twenty-two compact chromosomes are drawn into meta- 
phase (figs. 8, 9, and 10). 
The shape and size of these chromosomes vary from the large 
asymmetrically armed V’s to very small spheres. Intermediate 
between these two extremes are the hooked or J-shaped, the 
uniformly rod-shaped, the pointed rods or club-shaped, and the 
circular V’s or U’s of various shapes and sizes. 
Although definite pairs of chromosomes can readily be recog- 
nized in every clear spermatogonial metaphase plate, the arrang- 
ing of all the chromosomes into a paired series is very unsatis- 
factory. This is due principally to the fact that they vary 
somewhat in shape in different plates. Since the pairing is an 
arbitrary matter, the discussion on this point is confined to the 
larger pairs which are recognized with greater certainty. Pair 
‘A’ (figs. 8 and 9) is composed of large V-shaped chromosomes 
constricted at the base and increasing in size from that point 
outward. The arms seem to be about equal in size, but each 
possesses its characteristic shape (fig. 10); one is somewhat 
crooked, having the concave side inward, while the other is 
club-shaped. The arms normally stand about 10° or 20° apart, 
but the angle of divergence may vary from zero to 170°. The 
V’s which are opened widely are usually found with the apex at 
the periphery of the plate and with the arms extending left and 
right (fig. 13). They are ofttimes constricted at the apexes to 
such an extent that they appear, under low power, as two pointed 
rod-shaped chromosomes with the sharp ends touching. This 
condition is more often found when the arms of the V’s are 
pressed almost together. This accounts for the large number of 
plates that seemingly present twenty-three and twenty-four 
chromosomes. 
Although the hook (fig. 9, B) and pointed rod-shaped (fig. 9, 
C’) chromosomes vary, they are readily recognized as pairs. The 
former vary from straight rods to hooks, while the latter vary 
from pointed clubs to blunt rods. The characteristic shapes of 
the remaining chromosomes are not sufficiently prominent to 
warrant a comparative study. 
