MICHIGAN ACADEMY OF SCIENCE. 
103 
DIVISION OF THE SECONDARY SPERMATOCYTES. 
The chromosomes of the secondary spermatocytes are smaller and more 
compact than those of the first. Most of the nuclei examined had their 
chromosomes in the equatorial plate. The chromosomes appear as small 
blocks (Fig 1 . 16), presenting a very different appearance from those of 
the primary spermatocytes (Fig. 12). In a part of the nuclei the acces- 
sory chromosome appeal’s projecting out from one side of the plate (Fig. 
16). It is of course considerably larger than the other chromosomes. It 
divides with the rest and its chromatids pass with the others to the poles 
of the spindle. Since the accessory is larger and longer than the auto- 
somes its ends project down towards the equator of the spindle after the 
ordinary chromosomes have reached the poles. The division of the nuclei 
which do not contain an accessory is in all other respects similar to those 
which do. 
The result of the first spermatocyte division is the production of two 
secondary spermatocytes, one with an accessory chromosome and the 
other without. The secondary spermatocytes divide, the one without 
the accessory giving rise to two spermatids, neither of which contains 
an accessory chromosome; the other, with the accessory, giving rise to 
two spermatids each of which contains one of the chromatids of the 
accessory. Thus a single primary spermatocyte gives rise to four sper- 
matids, two of which contain an accessory chromosome and two of which 
do not. 
TRANSFORMATION OF THE SPERMATIDS. 
The chromosomes rapidly break down after the last spermatocyte 
division. At first they congregate in the nucleus in the form of a loose 
crescent and then become granular (Figs. 18, 19). There are small 
aggregations of granules around the nuclear membrane in many cases 
but these are not pronounced (Fig. 19). In the spermatids containing 
the accessory chromosome this chromosome can be recognized as a com- 
pact deeply staining oval body closely applied to the nuclear membrane 
(Fig. 19). It has much the same appearance that it had in the growth 
stages but it is of course smaller. Frequently two spermatids were 
found lying side by side, one with the accessory chromosome, the other 
without (Fig. 19). 
During transformation the spermatid gradually assumes a spindle 
shape and a tail is formed (Figs. 20, 21). At this time there is no ap- 
parent difference between spermatids with the accessory chromosome and 
those without. 
There appears in .the cytoplasm of the cells in the growth period a 
rounded or oval body which stains more deeply than the rest of the 
cytoplasm. This body can be traced throughout the growth period and 
also through the late spermatocyte stages and spermatid transformation. 
It is small during the growth but becomes a very large and conspicuous 
element in the spermatids. It is probably the Nebenkern (Figs. 18, 19). 
IV. DISCUSSION. 
The apical cell is such a large and imposing element in the follicle 
that it, should not lie overlooked. This seems to have been generally done 
by writers on Orthopteron spermatogensis. Davis (1908) however dis- 
