MUNSON: SPERMATOGENESIS OF PAPILIO. 
73 
In the preceding spherical condition of the spermatogones, the 
chromatin is in the form of a network with chromosomes arranged 
around the periphery, and an irregular chromatin mass near the 
center (pi. 13, fig. 24). Now the chromatin is all massed at the inner 
pole of the nucleus, close to the nuclear membrane (pi. 13, fig. 25). I 
have come to the conclusion that this is not the effect of reagents. It 
occurs in the best preserved material, and regularly in cysts of that 
particular stage. The nucleus shows no sign of shrinkage as it is 
regularly spherical. But owing to the massing of the chromatin at 
the inner pole of the nucleus, the latter has the appearance of a large 
vacuole (pi. 13, fig. 25). The chromatin then gradually expands into 
the vacant part of the nucleus, the chromatin strands growing out 
along the periphery, and finally turns out to be a much coiled single 
thread with regularly arranged small chromosomes (pi. 13, fig. 26). 
At first this coil appears near the periphery of the nucleus leaving a 
clear vacant space in the center. But this, too, becomes obliterated, 
and the nucleus finally presents the appearance represented in plate 
13, figure 27. The cells have now again become spherical (pi. 13, figs. 
26, 27), the nucleus has increased in size causing the cytoplasm to 
appear less abundant than in the first synaptic stage (pi. 13, fig. 
27) . The chromatin is now again in the form of a network, but the 
linin fibers are very delicate, and intersect one another at variable 
angles. At these points of intersection, the spherical chromosomes, 
now greatly reduced in size, are found. The whole network has the 
appearance of being in a state of tension, caused by the expansion of 
the nucleus (pi. 13, fig. 27). 
These cells now proceed to divide mitotically. Two centrosomes 
each with an indistinct aster appear at the opposite poles of the nucleus; 
the nuclear membrane disappears, and the nuclear contents are con¬ 
verted into a spindle (pi. 13, fig. 28). The chromosomes are arranged 
at the equator of the spindle. They are spherical and apparently 
single (pi. 13, fig. 28, a). They soon split (pi. 13, fig. 28, b ). Each 
half chromosome moves to its respective pole (pi. 13, fig. 28, c). I 
have seen only one fiber attached to each chromosome. As the halves 
separate, the intermediate fibers connect the halves, but these fibers 
seem much more delicate than the original spindle fibers (pi. 13, fig. 
28) . I shall refer to this, again in connection with the maturation 
division, some phases of which are represented in plate 13, figures 29, 
30, 31. I feel certain that figures 25, 26, and 27 represent prophases 
