The Spermatogenesis of Aplopus mayert. 23 
lent chromosomes of the equatorial plates of the first maturation mitosis 
and pairs of chromosomes of the spermatogonial stages can be found, but 
these are hardly of sufficient precision to seem convincing in support of the 
theory of the individuality of the chromosomes or to add anything con- 
firmatory of the selective character of synapsis. 
The accessory chromosome in Aplopus, it will have been noticed, passes 
undivided to one of the poles of the first maturation spindle. In the late 
telophase and during the stages when the daughter-nuclei are formed and 
the ordinary chromosomes pass into the nuclear reticulum, the accessory 
becomes more or less bipartite, but always retains its sharp contour and 
deep-staining reaction and its usual position in close connection with the 
nuclear wall (figs. 92, 93, 94, 95, and 96). The accessory chromosome 
still retains these distinguishing characteristics throughout the resting stage 
(fig. 97), which is interpolated between the two maturation mitoses, as well 
as during the early prophase of the ensuing division. At this stage the cyto- 
plasm of the secondary spermatocyte also frequently contains several larger 
or smaller masses of eliminated chromatin. Obviously only one-half of the 
secondary spermatocytes resulting from the previous division can have the 
accessory chromosome. Study of many sections shows without a doubt that 
only about one-half contain the chromatic body (or any body that reacts to a 
selective chromatin stain) which we have identified as the accessory chromo- 
some. Figures 101 and 102 show two secondary spermatocytes side by side, 
one with the accessory chromosome and the other without it. 
According to the several investigators, there is variation among the 
Arthropoda in regard to the time when the accessory chromosome divides, 
1. e., in the first or second mitoses. McClung (1900 and 1902b), in the case 
of several Orthoptera, has traced the accessory back into the spermatogonial 
rest-stages, and finds that it subsequently divides only in the first sperm- 
atocyte division. Baumgartner (1904) in Gryllus domesticus, Stevens 
(1905) in Stenopelmatus and Blatella germanica, and Otte (1906) in 
Locusta viridissima find that this chromosome divides in the second division 
instead of the first. Moore and Robinson (1905) claim that the accessory 
in Periplaneta americana is only a plasmosome that dissolves before each 
division and is reconstructed after it. This can not be the case in Aflopus. 
No indication of a true nucleolus (plasmosome) can be demonstrated by 
any of the several staining methods employed in any of the cells in the 
line of the spermatogenesis. 
SECONDARY SPERMATOCYTE. 
The prophase stages of the second maturation division present nothing 
extraordinary. The succession of events is similar to that of the sperm- 
atogonial division and an ordinary homeotypic mitosis, with the exception 
of the presence of the accessory chromosome. ‘The latter never passes into 
