WILCOX: SPERMATOGENESIS OF CALOPTENUS FEMUR-RUBRUM. 195 
are shown in Figures 53, 56, 76, and 78. In Figure 78 (Plate 3) at the 
upper end of the cell is seen a body which, from its position, stainabil- 
g after the second 
ity, and size, I believe to be the centrosome remaining 
spermatocyte division. Below it lies the nucleus without as yet a limit- 
ing membrane, but containing a deeply stained body within the ring- 
like group of chromosomes. The remains of the interzonal filaments 
extend from near the nucleus to the cell membrane opposite the sup- 
posed eentrosome. At the distal ends of these fibres are some very fine 
stainable granules. 
Let us now consider separately the history of each of these structures, 
centrosome, nucleus, and interzonal filaments. 
The centrosome comes ultimately to occupy a position between the 
nucleus and the modified remains of the interzonal filaments. It ap- 
parently moves around the nucleus through an are of 180 degrees. 
Figures 78, 80, 79, 81, 82 (Plate 3) illustrate this migration of the 
centrosome. I could not find evidence of the division of the centro- 
some until later stages in metamorphosis, such as those shown in Fig- 
ures 97-100. The centrosome manifests its double nature with varying 
degrees of distinctness in the stages last mentioned. Afterwards the 
two parts fuse into one, and the whole body elongates, as represented 
in Figures 109 and 110. In subsequent stages the chromatic substance 
of the head of the immature spermatozoón becomes more compact, and 
stains so much like the centrosome that it is difficult to mark the limits 
of the two substances. 
The chromosomes, as was shown in my previous paper on this subject 
(95), soon fuse into à more or less homogeneous mass, which takes on 
a crescentic shape, leaving in the nucleus at first a rather large vacuole, 
which is located next to the centrosome or neck-body. One end of the 
crescent becomes applied to the centrosome, and the whole head elon- 
gates, crowding the vacuole to one side. The vacuole finally disappears, 
and the chromatic substance in consequence of condensation stains more 
deeply. 
The remains of the ¿nterzonal filaments immediately after the second 
division of the spermatocyte are shown in Figure 78. We find that at 
this stage it consists of an elongated striate body composed very evi- 
dently of distinet fibres. This oblong fibrous body, which is to become 
the “ Nebenkern," contracts longitudinally, so that the distal ends of 
the fibres are drawn away from the cell membrane (Figs. 56, 77). The 
ends of the Nebenkern round themselves off (Fig. 84), and the sperma- 
tid soon reaches the stage represented in Fignres 54, 55, 80-83. The 
