450 WILLIAM M. GOLDSMITH 
The rods are shorter and thicker, the U’s are more bean- or kid- 
ney-shaped, and the conspicuous V’s are more widely open. 
These changes are due, no doubt, to the increased pressure and 
to the crowded condition. 
5. GROWTH PERIOD OF THE PRIMARY SPERMATOCYTE 
The spermatogonial telophase chromosomes, though drawn 
out and confused, show in cross-section a certain degree of in- 
dividuality (fig.15b). At this pot they still appear somewhat 
compact, but readily change to a woolly appearance (fig. 16 b). 
In the earliest growth period the chromatic material presents 
itself as faint, delicately coiled threads, having no perceptible 
limiting membrane (fig. 17). Only under the most favorable 
conditions are the sex-chromosomes discernible. During the 
formation of the leptotene stage these fibers increase in size and 
staining reaction, and thus present a very crowded nucleus 
(figs. 18 and 19). The entire mass of chromatic threads now 
gradually contracts and culminates in a typical synaptic knot 
(figs. 20 and 21). This is usually spherical and lies against the 
nuclear membrane which made its appearance in the late pre- 
synaptic stage. In some cases the synaptic knot is very irregu- 
lar or flattened (fig. 20) and extends across the central part of 
the nucleus. Here, as in case of the majority of presynaptic 
leptotene nuclei, the chromatin nucleolus cannot be identified 
with certainty. 
The postsynaptic pachytene is inaugurated by the gradual 
loosening of:the chromatic fibers of the synaptic knot. The 
outer loops, which seem to persist throughout synizesis, first 
recede from the chromatic bundle, giving room for the loosening 
of the central fibers. This proceeds until the nucleus is again 
crowded with chromatic threads (figs. 25 and 26), much coarser 
and less numerous, however, than in the former leptotene nucleus. 
A number of instances were noted in which the chromatin fibers 
did not loosen from the synaptic knot. In these cases practically 
the entire nuclear content formed a very dense sphere, and then 
the entire cell degenerated (figs. 23 and 24). As the nucleus 
