MUNSON: SPERMATOGENESIS OF PAPILIO. 
91 
into the nebenkern (pi. 16, fig. 121), there are various reasons for 
believing that its persistence is due not only to the fact that the central 
spindle fibers are derived directly from the chromosomes, causing 
their considerable diminution in size, but also to the fact that chromatin 
granules are separated off from the chromosomes as they move toward 
the poles. Occasionally entire chromosome segments seem to be 
left behind (pi. 16, fig. 119; pi. 13, fig. 31). Often a few straggling 
chromosome segments are found scattered along the spindle fibers 
(pi. 13, fig. 31; pi. 16, fig. 118), or else drawn out into stainable threads 
parallel with the spindle fiber. 
It seems to be the presence of this chromatin gradually shed or 
eliminated along the path as the chromatin segments approach their 
respective poles, which gives the nebenkern its staying power. 
Relation o / nebenkern to nucleus .— I have been led to believe that 
in mitosis of the spermatogonia, the connective fibers are reabsorbed 
bv the nucleus as it expands, and that it does not merely disintegrate. 
The nucleus in those cases is active, fully re-formed after each mitosis 
as the cell also seems to grow. The nucleus becomes large occupying 
a considerable part of the cell. 
At the completion of the last maturation division, too, the nucleus 
is partly re-formed, but it is different from the original nucleus. It 
never becomes so large and rich in nucleoplasm as the nuclei of the 
spermatogones (compare fig. 24 with fig. 39a or with fig. 32, pi. 13). 
I consider this failure on the part of the nucleus to regain its original 
size and to acquire a larger supply of karyolymph as evidence of its 
declining functional activity. This is suggested partly by the fact 
that no further mitosis is to occur. 
In my work on Limulus (Munson, ’ 98 ) and also in that on the 
tortoise (Munson, ’ 04 ), I was led to conclude that karyolymph is 
produced inside the chromatin masses especially in the chromatin 
nucleoli of the oocyte; and that it is secreted or extruded by these 
chromatin masses. Thus it accumulates between the chromatin 
granules, causing the whole nucleus to expand. The large expanded 
state of the nucleus is therefore, in my mind, evidence of nuclear 
activity. It may be worth while considering whether the comparative 
inertness of the chromatin mass, after the last maturation division, is 
not responsible for the persistence outside the nucleus, but in close 
contact with it, of the nebenkern. The lagging behind of some 
chromosomes may be another evidence of this inertness. 
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