86 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
6. The centrosome is extremely minute, a mere clot at the point 
of convergence of the astral rays. 
7. The centrosome is surrounded by three circles of microsomes, 
which are so related to the astral rays that they appear like consider¬ 
ably enlarged cytomicrosomes. 
8. The nuclear membrane persists long after the asters are formed. 
9. The theory of the individuality of the chromosomes is well 
sustained in these sperm cells. 
10. It seems to me that the chromosomes can be traced from the 
primary spermatogone to the fully developed sperm cell. 
11. The nuclear linin forms a network with which the chromosomes 
are associated. 
12. From what I have seen, I believe that the chromatin and 
linin are intimately related; that the smaller granules in the linin, 
forming the stainable nuclear network, resemble the cytomicrosomes, 
and may in certain states of the linin be added to or subtracted from 
the chromosomes, causing them to vary in size. 
13. In a state of nuclear rest, the granules separate from the 
aggregated chromosome, and become scattered along the linin fiber, 
which thus appears granular and stainable. 
14. On approaching mitosis, the granules all flow together into 
their respective large stainable chromosomes, which are united by 
the clear linin substance, appearing now as if stretched. 
15. From this stretching there results a single chain of chromo¬ 
somes arranged around the periphery of the nucleus. 
16. This thread becomes folded by sinking together of the whole 
chromatin substance at one pole of the nucleus. 
17. Out of this compact mass there emerges a double thread, 
spireme, partly doubled a second time. 
18. As the second doubling progresses, there results a thread of 
four series of chromosomes, seven in a line. 
19. This thread finally breaks up or rather separates between 
each chromosome giving rise to seven groups of four chromosomes, 
tetrads. 
20. By continued separation, the four chromosomes of a tetrad 
are separated into two groups, diads. 
21. Tetrad formation here is consequently a temporary conjuga¬ 
tion of chromosomes, in which there may be an exchange of constit¬ 
uent granules or ids. 
