24 
SPERMATOGENESIS OP NORMAL 
which at times a delicate network is visible. Occasional par¬ 
ticles of chromatin may be scattered about in it (Figs. 10, 13). 
THE SECONDARY SPERMATOCYTES AND THEIR DIVISION. 
The product of the division just discussed consists of two 
cells which are of considerably smaller size than the primary 
spermatocyte itself and which never attain to its volume. Their 
nuclei, too, are smaller than the parent nucleus and compare 
more nearly in size with those of the spermatogonia. These 
cells are the spermatocytes of the second order, or secondary 
spermatocytes. A distinct resting stage occurs in some of the 
secondary spermatocytes at least, but this may not be true for 
all. It is a very transient condition, however, and the cell pro¬ 
ceeds almost immediately to division. 
In the preparation for division there is nothing which corre¬ 
sponds to the collapse of the nuclear material in the primary 
spermatocyte, nor is there formed at any time a well marked 
spirem. The chromatin seems to pass rapidly from the ap¬ 
parent resting condition into one where it exists as distinct 
chromosomes. It is very easy to find numerous cells in process 
of division, but the stages preparatory to division are rarely 
seen. This would lead to the conclusion that perhaps in some 
cases the chromosomes rearranged themselves for the second 
division without passing through a resting stage. 
When the chromatin takes on the form of chromosomes, 
curiously enough only four rings or vesicles appear instead of 
eight, as seen in the primary spermatocytes. This number 
persists and as a result only four chromosomes come to the 
equator when the spindle is formed (Fig. 14). Occasionally a 
spindle bearing eight chromosomes of a smaller size is to be 
found. The writer was unable to decide whether such a type 
belongs also to the secondary spermatocyte or whether re¬ 
agents have simply caused an unusual shrinkage in the chromo¬ 
somes of the primary spermatocyte. 
The formation of the spindle and the attachment of the 
chromosomes to it occurs in much the same manner as in the 
primary spermatocytes and will require no detailed discussion. 
The final size and appearance of the individual chromosomes is 
practically the same as that of the bivalent chromosomes of 
