90 JOSE F. NONIDEZ 
from that of the M-chromosomes. When the prochromosomes 
are condensing the X-chromosome appears as a V- or J-shaped 
body (fig. 67, cell to the left); once the massive condition of the 
former is reached, it becomes looser in structure, finally unravel- 
ing in a thick, coarse thread of ragged outline (figs. 68, 69, and 
70, a). A condensation follows and the deeply stained body of 
later stages is formed. The process of condensation must take 
place rapidly, since I have not been able to find stages leading to 
this condition. Even when found it would be very difficult to 
decide whether condensation or unraveling is taking place. 
It may happen that one of the M-chromosomes also unravels 
at this time, or at least becomes looser in structure (fig. 70, /); 
perhaps this is but the result of deferred condensation. The 
close proximity of this M-chromosome and the X-chromosome in 
the figure and their connection by means of delicate fibers is 
suggestive of an influence of the latter on the M-chromosome, 
but conclusive evidence on this point is lacking, since this appear- 
ance is far from common. 
The M-chromosomes, and probably also the small chromo- 
somes, behave from this moment like the euchromosomes, so far 
as the unraveling process is concerned. When the latter begin 
to unravel, the M-chromosomes become looser in structure, and 
each gives rise to a tightly convoluted thread which, on account 
of its considerable length, spreads throughout the nuclear cavity. 
Two details of the unraveling process are shown in figure 76; in 
figure 78 the leptotene M-chromosomes still exhibit a wavy ap- 
pearance which is less conspicuous in those of figure 77. It is 
very difficult to follow the unraveling of the small chromosomes, 
since in most of the cases the X-chromosome, to which they are 
united, lies in the mass of chromosomes located in one of the 
nuclear poles. 
It is an interesting fact that the M-chromosomes preserve their 
original thickness during the early pachytene condition and ap- 
pear as separate individuals connected with the X-chromosome 
by one of their ends. A comparison of figures 77 and 78 (which 
represent the leptotene stage) with figures 79 and 80, which are 
nuclei in the early pachtyene stage, shows this condition very 
