517 
chromosomes are handled during the later maturation processes it is 
impossible definitely to determine. 
The large number and small size of the chromosomes, and their 
tangled compact condition during the maturation mitoses (figs. 20 
to 22), renders satisfactory detailed observation impossible. It may 
be definitely said, however, that there appears no evidence of a special 
chromosome among the mass. In no case was a chromosome distinctly 
marked by unusual size or by premature passage to the pole. Fig. 20 
represents the sole instance in which at metaphase a chromosome was 
even slightly differentiated by position and size among the ordinary 
Figs. 16 and 17. Early postsynapsis stages. The nuclear thread appears to con- 
sist of bi-serially arranged chromatic granules. The persisting chromosome nucleolus 
(accessory chromosome) is commonly bipartite, but placed without reference to the 
idiozome. 
Fig. 18. Early prophase. The split thread is beginning to segment. The more 
peripheral ends are becoming chromatic first. The idiozome shows a centrosome. The 
accessory chromosome is still very conspicuous. 
Fig. 19. Prophase stage of first maturation mitosis. The accessory chromosome 
is clearly discernible among the less chromatic, mossy, split, ordinary chromosomes. The 
latter become chromatic first at the end attached to the nucleus wall. 
Fig. 20. Metaphase spindle of dividing primary spermatocyte. The outlying 
larger chromosome may be the accessory. This is the only instance among many similar 
stages where such a differentiating position obtains. In all other instances the accessory 
chromosome remains indistinguishable among the ordinary chromosomes. 
Fig. 21. Metaphase plate of similar stage. The chromosomes are numerous, small 
and closely massed. The accessory cannot be identified. 
chromosomes. The chromosome here indicated may possibly be the 
accessory; and show a weak tendency to behave at the first mitosis 
like the typical accessory chromosome of certain insects. 
Since no resting secondary spermatocytes appear, the usual evi- 
dence respecting nuclear dimorphism at this stage can not be adduced. 
