922 THE AMERICAN NATURALIST. [Vor. XXXV, 
more distinct and aggregated into separate threads joined 
together by linin. The manner of their origin again lends 
support to the view concerning their individuality in the resting 
cell. By a gradual process of condensation sixteen compact 
masses of chromatin are produced. These 
sixteen masses are of various forms. Some 
---f--8 are dumb-bell-shaped, two spheres of chro- 
matin joined together by linin ; some are 
hu crescent-shaped, and stil others are more 
oe or less complete rings (Fig. 3). The differ- 
oS ent forms may occur in the same nucleus, 
but apparently without constancy in the 
3 ratio of relative frequency of occurrence. 
Two main types may be distinguished 
nid Ps sual dor among the chromosomes according to their 
hens m (diag structure and mode of origin; z.e., (1) those 
in which the bivalent chromosome consists 
of two univalent chromosomes lying end to end, as in those 
having the dumb-bell shape; and (2) those in which the 
univalent chromosomes lie side by side, as in those arising 
through a ring or narrow V-shape. A form intermediate 
between these is represented by those having a crescent shape. 
The different types and their probable mode of origin are shown 
in the diagram (Fig. 3). 
In the equatorial plate of the first maturation division the 
two forms may again be seen. In sections stained with iron 
haematoxylin and strongly decolorized a longitudinal split is 
distinguishable in the chromosomes. In the 
dumb-bell-shaped chromosomes this lies par- 
allel to the long axis of the spindle, but in the 
others more or less oblique to it, or at right 
angles to it (Fig. 4). In the spermatogonic p. 4. — Equatorial plate 
divisions, on the contrary, as is shown in prep- of tha bea 
arations similarly treated, the longitudinal 
split lies transversely to the long axis of the spindle (Fig. 5). 
Karyokinesis separates originally distinct chromosomes, and 
the first maturation division is therefore reducing. In many 
cases the chromosomes can be seen to be composed of a 
