288 



synapsis (Figs. 13—16) the chromosomes again dispose themselves into 

 a reticulum of broad threads more or less chromatic, sometimes giving 

 indication of a longitudinal fission, and arranged in lattice-work fashion. 

 The accessory meanwhile closes up and shortens down into a compact 

 chromatic body with sharp contour closely applied to the nuclear wall 

 (Fig. 16). 



Between the latter stage and early prophase of the first maturation 

 division a stage is interpolated somewhat resembling a resting phase. 

 The lattice-work arrangement of the nuclear spireme is lost having 

 changed into an irregular pale-staining network of fine mesh and fiber 

 and with frequent karyosomes (Fig. 17). The accessory at this stage 

 is frequently bipartite. The nuclear network presently again becomes 

 arranged into a wide pale-staining spireme. This breaks up into a 

 number of segments (17) among which the accessory is always very 

 conspicuous by virtue of its intense chromatic character and definite 

 outline as a spherical, bipartite or even quadripartite body (Fig. 18). 

 The pale mossy chromosomes next sutfer a longitudinal split which is 

 closely followed by a transverse split thus forming typical tetrads. 

 The accessory lies among the tetrads, frequently with a characteristic 

 U-shape (Figs. 19 and 20). Later stages show all the chromosomes 

 highly chromatic and with sharp outlines most of them in various tetrad 

 forms (Fig. 21) among which the accessory is only occasionaly recog- 

 nizable by its larger size, compact condition or U-shaped form. 



Figure 22 shows metaphase chromosome groups of four contiguous 

 primary spermatocytes. All of the cells show 18 chromosomes, the 

 full postsynaptic count. The accessory can not be definitely dis- 

 tinguished in these groups, but it is undoubtedly one of the larger 

 eccentric bodies. The accessory is unmistakeably shown to the right 

 of the group (18) in Figure 23. Figure 24, shows the arrangement of 

 the chromosomes in the spindle and their general shape at metaphase. 

 The accessory is seen as a large U-shaped body near one pole. The 

 later stages of the first maturation mitosis (heterotypic) are seen in 

 Figures 25 to 30. The ordinary chromosomes are of various shapes in- 

 cluding dumb-bells, rods, clubs and short golfstick-like bodies; and they 

 range in size from very small to very large elements. The accessory 

 chromosome passes undivided to one of the poles, always precedes the 

 ordinary chromosomes, and usually lies to the side of the latter. It 

 appears to be connected to only portion of a spindle fiber. 



Study of the chromosomes from the tetrad stage of prophase 

 through metaphase and anaphase shows that they separate in the first 

 mitosis along the plane of the second prophase split, and if this split 



