12 
W. E. AGAR. 
condensation has been unrestricted than in another where its 
entanglement with other threads acting as relatively fixed 
points has kept it stretched thin. 
The direct evidence for this mode of syndesis is to be found 
in the zygotene nuclei, such as PL 1, fig. 10, for example, 
where there is no doubt that the threads in the unorientated 
part of the nucleus are of the same order of thickness as the 
incompletely fused moieties of the pachytene threads. 
As a result of their work on Tomopteris, Salamandra, 
Spinax, and Myxine, the Schreiners think that they can 
fo rmulate the hypothesis that chromatin granules are present 
in the same number in homologous chromosomes, and that 
conjugation consists essentially in the fusion of these 
granules in pairs. The evidence presented by Lepidosiren 
is negative in this respect. As a rule the conjugating threads 
do not present any granulation, this making its appearance 
in the pachytene stage (see PL 2, figs. 13, 14, and 15). 
In PL 1, fig. 10, it is true we do see one pair of threads 
each with three large chromatin granules which are about to 
fuse together. This condition is, however, not the rule but 
the exception. It may be that the general absence of 
chromatin beads in the conjugating threads is due to the 
fact that in Lepidosiren conjugation takes place very early, 
i.e. while the threads are still extremely long and thin. 
For it is possible that the granules are really present but so 
drawn out as not to be readilv demarcated from one another. 
•/ 
Their appearance in the later stages of the pachytene nucleus 
would then be explained by the continuous contraction of the 
threads, whereby the granules are enabled to assume their 
spherical shape. 
In PL 2, figs. 13 and 14, conjugation has proceeded farther 
and the arrangement of the pachytene threads in the charac- 
teristic bouquet is becoming apparent. Fig. 13 is drawn 
from the side, fig. 14 from the pole. In fig. 13 many of the 
threads show no sign of doubleness, but in some of them 
their leptotene constituents diverge and run separately for a 
considerable distance. In the nucleus figured in fig. 14 
