THE SPERMATOGENESIS OF DOMESTIC MAMMALS. 361 
Post-synaptie stage :—The conjugated chromosomes as stated above 
gradually move towards the center of the nucleus, while the bulk of the 
cell increases. 'These proceed more and more until the chromatin spireme 
spread slowly throughout the nucleus, becoming more loosely situated, the 
individual filament growing thicker but staining fainter. 
During the Post-synapsis the accessory chromosome retains its staining 
capacity and its sharp contour (Figs. 20—22). Fig. 20 is drawn from a strongly 
destained preparation where the accessory chromosome is stained intensely with 
iron-haematoxylin while the chromatin spireme is very faintly stained. In 
the post-synapsis the accessory chromosome usually remains in contact with 
the nuclear membrane and generally appears oval, it varies in size and form, 
sometimes being heart-shaped and occasionally distinctly bipartited (Figs. 
22—28). 
In the growth stage one, two or sometimes three small deeply stained 
granules make their appearance in the cytoplasm (Figs. 22, 23, 25), these 
are similar in form and behavior to those described by Wırson (’13) in 
Pentatoma. 
In the primary spermatocyte the idiozome is a conspicuous body, placed 
close to the nuclear wall (Figs. 19, 20, 21, 22, 25, 26). During the synapsis 
it takes its position at the pole of the nucleus, where the chromatin spireme 
converges (Figs. 18, 19). It has not, however, a distinct boundary, and is 
represented only as an oval or a round mass. It does not change its position 
in the early post-synapsis but becomes homogeneous in its appearance (Figs. 
19, 20). In the prophase of the first reduction division, it is divided into 
two small spheric bodies which gradually move apart from each other. During 
the synapsis and post-synapsis the centrosome, with rare exceptions, can not 
be! found within the idiozome (Figs. 22, 25, 26). 
Prophase :—Finally the spiremes become shortened in length, and form 
many variously curved chromosomes, but the rings or loops as described 
in other forms at this stage do not appear (Figs. 28—30). Meanwhile 
the idiozomes begin to disintegrate, becoming more and more granular, 
while the centrosome appears distinctly close to the nuclear wall (Fig. 29). 
This latter soon disintegrates and the chromosomes arrange themselves in the 
metaphase plate (Figs. 31). 
