AND OF HYBRID PIGEONS. 
21 
one or two violet staining nucleolar-like masses of linin exist 
independently in the nucleus (Fig. 9). 
Further preparation for division is seen in the gradual con¬ 
densation of the elongated rings into a shorter and heavier 
type. The chromatin becomes fused together gradually in such 
a way that the distinct granules are no longer visible. It is not 
unusual, after the condensation has proceeded for some time, 
to see some of the rings in the form of a four-partite structure 
as shown in Fig. 10, tr., where in one of the chromosomes to the 
right, four more or less spherical densely staining areas con¬ 
nected by lighter bands of linin are visible. This is by no 
means universal. It is possibly to be compared to the tetrad 
formation so frequently observed in maturation phenomena, 
such a chromosome is strikingly similar in appearance to the 
tetrad types pictured by vom Rath^ for Gryllotalpa, or Wilcox^ 
for Caloptemus. It might be well to mention here, also, that in 
the primary spermatocytes of hybrids in some instances, one 
or more of the large chromosomes was observed to consist of 
four small closely apposed rings or vesicles (Fig. 35). 
When the final condition of chromosome formation is at¬ 
tained, the chromosomes exist as eight thick rings. Examin¬ 
ation under high power shows that each ring consists of a 
thread or shell of chromatin encapsuled in a film of linin. If the 
preparation is not sufficiently decolorized after staining with 
haematoxylin, the chromosome will have the appearance of a 
small black disc or globule, its ring-like nature being entirely 
obscured. 
The chromosomes, after completing their development, 
gradually arrange themselves along the thick nuclear wall (Fig. 
10), as in the corresponding stage preparatory to division in the 
spermatogonia. A residue or condensation of linin material 
forming a nucleolar-like mass may be present near the center of 
the nucleus. 
By the time the nucleus has assumed this arrangement, the 
fibers of the spindle have become much more distinct and 
spread around the nucleus from either pole toward the equator 
1. vom Rath, O: Zur Kenntniss der Spermatogenese von Gryllotalpa vul¬ 
garis.—Arch. f. mlkr. Anat., XL, 1892. 
2. Loc. cit., p. 12. 
