84 JOSE F. NONIDEZ 
of the chromatin contents due to the unequal distribution of the 
chromosomes of the X-complex during the reductional mitosis. 
2. The growth period 
The absence of a confused or reticular stage in the growing 
spermatocytes makes possible the recognition of independent 
chromosomes throughout the greater part of the growth period. 
No attempt has been made to trace in detail the history of the 
euchromosomes, but their condition in the different stages is 
described for comparison with that of the chromosomes of the 
X-complex. The behavior of the latter is extremely interesting 
and stands in sharp contrast with that of the euchromosomes, 
since they are brought together slightly before synapsis, but re- 
main independent to some extent forming a loose complex, with- 
out being actually paired and, therefore, show their univalent 
nature throughout the postsynaptic stages. 
The presynaptic stages can be classified as follows: 
a. The resting stage, which is but an extended telophase of 
the last spermatogonial mitosis, the nuclei closely resembling in 
structure those of the spermatogonia. 
b. The prochromosome stage, during which the chromosomes 
appear as massive bodies located near the periphery of the 
nucleus. 
c. The synizesis stage, in which the prochromosomes move to 
that pole of the nucleus which is nearest the sphere and centro- 
some, as in the ordinary contraction figure. 
d. The unraveling stage, representing the transition between 
the prochromosomes and the leptotene threads, the chromosomes 
appearing as convoluted threads. 
e. The leptotene stage, in which thin threads occur. 
Stages a and ¢ are highly characteristic of Blaps. The pro- 
chromosomes have been described several times in animals, but 
in no case, I believe, has synizesis been described when the chro- 
mosomes are in such a condition. 
Synapsis probably takes place when the leptotene stage is 
reached, but on account of the crowded condition of the chromo- 
