PLATE 2 
EXPLANATION OF FIGURES 
First spermatocytie division—Continued 
19 to 23 The formation of a double spireme completed (zygotene stage). 
There is a peculiar chromatin body in the nucleus at this stage, as is represented 
by the nucleolus-like structure in figures 19, 20, and 23, or by a modified portion 
of the spireme in figure 22. The exact nature of these structures has not been 
worked out, although their genetic relation with accessory chromosomes seems 
very probable. 
24 to 26 Breaking up of the spireme into segments (pachytene stage). The 
segments are in reduced number. 
27, 31, and 32. Halves of each spireme segment bending toward each other, 
the original split of the spireme is clearly recognizable (pachystreptotene stage). 
28, 29, and 30 Transformation of spireme segments into tetrads; the narrower 
lateral split in the tetrads undoubtedly corresponding to the original split of 
the spireme. 
33 A cell entering the metaphase. 
34 Metaphase spindles. The split of the early spireme is still visible on the 
chromosomes. 
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