The nuclear compoueuts of the sex cells of four species of cockroachea. 499 
7. The spermatid and the spermatozoön. 
The writer bas not attempted to investigate the various structures, 
such as the nebenkern, the acrosome, the mitochondria and the axial 
filament of the spermatid and spermatozoa, but rather to confine 
himself to the history of the odd chromosome and the plasmosome 
duriug these stages. It will be necessary, however, to dwell upon 
these formier points to some extent to describe the behavior of the 
nuclear components. 
When the axial filament of the "tail” of the spermatid begins 
to grow out (fig. 47) and the nucleus is loeated excentrically in the 
cell, the odd chromosome is still to be seen as a very deeply 
staining body in the center of the nucleus in the midst of the threads 
represeuting the ordinary chromosomes. At the same time, the plas- 
mosome may be seen lying outside of the nuclear wall. There is, 
generally, a smaller deeply staining body lying near the plasmosome 
which gives one the impression that the latter is disintegrating. This, 
however, is not the case, for the plasmosome separates from this 
body, still retainiug its original size. At a later Stage, the plasmo- 
some may be seen to have moved distally (fig. 48) away from the 
nucleus. This cell (fig. 48) shows no odd chromosome. A still later 
stage of the spermatid is represented in figure 49 where the odd 
chromosome may be readily seen within the nucleus, while the plas- 
mosome lies farther away from the nucleus than before. The envelop 
of the axial filament of the spermatid is forming and the plasmosome 
lies on its outer border. The formation oft these structures, however, 
does not take place invariably at the same time witli respect to the 
migration of the plasmosome, as will be seen in figure 50. Here 
the plasmosome lies away from the axial filament at the edge of the 
cytoplasm. The odd chromosome is still visible, although the nucleus 
has become much more compact and darker, rendering a clear dis- 
crimination of the structures within it more and more difficult. The 
condeAsation of the nucleus continues (fig. 51) and the maximum 
depth of staining is assumed by it. Now the nuclear structures 
begin to fade so that they may be distinguished only with difficulty 
in the following stage (fig. 52). In the meantime, the plasmosome 
has migrated down through the cytoplasm until it has reached the 
middle of the "tail” where it lies in a small collection of cytoplasm. 
Finally, in the fully formed spermatozoön (fig. 53), it may be seen 
for a time lying in this position and when at last the collection of 
