SS JOSE F. NONIDEZ 
M-chromosomes, which also undergo a process of unraveling. In 
Side views of the nucleus all that can be seen is a mass of closely 
interwoven threads from which some filaments emerge, spread- 
ing in the nuclear cavity (fig. 78, left of the nucleus), but on the 
whole they remain crowded at the pole nearest to the sphere. 
A comparison between the euchromosomes and M-chromosomes 
fails to show any other difference than the greater length of the 
latter. 
Synapsis. Observation of the actual pairing of the euchro- 
mosomes to form the pachytene threads is exceedingly difficult 
in Blaps on account of the contraction of the chromatin and, in 
spite of several attempts to solve this question, no positive re- 
sults could be obtained. It is true that here and there it is pos- 
sible to find parallel leptotene threads which might be regarded 
as the early zygotene condition, but the Y figures, so conspicuous 
in the nuclei of the spermatocytes of other animals, and the pro- 
gressive formation of thick threads by the close association of a 
pair of leptotene threads could not be detected in my material. 
The question of synapsis is therefore unsettled, so far as the 
euchromosomes is concerned. Judging from the clefts occa- 
sionally seen in the euchromosomes during the early pachytene 
stage and the longitudinal split seen before the prophase of the 
first maturation division, some ground is given for the belief 
that parasynapsis takes place. 
B. Postsynaptic stages. f. Early pachytene stage. Nuclei in 
this stage are found in cysts containing spermatocytes in the 
leptotene condition. The stage is characterized by the presence 
of thick rods, straight, slightly curved, or very often V-shaped. 
In a few of these rods (fig. 80) a longitudinal cleft or space may 
be detected, which seems to correspond to a place in which the 
conjugating chromosomes are still separated. In slightly later 
stages this cleft disappears, the euchromosomes becoming thick 
and continuous throughout (fig. 79). 
As a result of the pairing of the chromosomes, the dense con- 
dition of the synaptic knot gives way to a somewhat looser mass 
which begins to spread slowly throughout the nuclear cavity. 
There is no definite orientation of the chromosomes at this stage. 
