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as also by their more chromatic nuclear reticulum, spheroidal or poly- 

 hedral form and by the presence in the resting stage of the accessory 

 chromosome. This latter structure takes a characteristic position close 

 to the nuclear wall. It assumes various shapes: spherical, frequently 

 oblong, sometimes bipartite and occasionally even skein-like. As many 

 as seven generations of secondary spermatogonia have been determined. 

 The number of chromosomes here again is 35 (Fig. 4). None of these 

 can be satisfactorily identified as the accessory through a large 

 U-shaped body may possibly represent this structure (see Fig. 4). 

 Figure 5 shows the character of the spindle and chromosomes at meta- 

 phase. The division is of the typical homeotype mode. In Figure 6 

 is given an equatorial plate of a dividing follicle cell of the ovary. The 

 chromosome group numbers 36. 



The accessory chromosome cannot be satisfactorily traced through 

 the late teleophase of the spermatogonial divisions — it does not 

 appear to persist as a chromatic sharply contoured body, but assumes 

 more or less the character of the ordinary chromosomes until the 

 resting stage is re-attained — until the final division (Fig. 7) pre- 

 ceding the first order of spermatocyte cells. In the late telophase of 

 this generation of spermatogonia it retains its morphological integrity 

 and deep staining capacity among the pale-staining mossy ordinary 

 chromosomes. It is usually club-shaped or bilobed at this period. 



A brief resting stage (Fig. 8) ensues before the stage of synapsis. 

 Here the nuclear reticulum is again pale-staining with occasional karyo- 

 somes and the accessory has its characteristic position near the nuclear 

 wall. It may be spherical, bilobed or bipartite at this stage. The 

 primary spermatocyte now enters upon its growth period. It enlarges 

 but slightly in size, however, and the cytoplasm always remains sparse 

 in amount. Meanwhile the chromatin seems to increase considerably 

 in bulk. Presently great activity and decided alterations transpire in 

 the nuclear reticulum. Coincidently the accessory chromosome elon- 

 gates into a rod or club-shaped body (often giving indication of a 

 longitudinal split) attached by its lesser end to a slightly chromatic, 

 broad spireme arranged in lattice-work fashion (Fig. 9). This spireme 

 increases in chromatin content, and segments into a number (34?) of 

 parts which arrange themselves in the form of short loops at one pole 

 of the nucleus (Fig. 10). This represents the synizesis stage. The 

 next step involves the opening up of these loops by the freeing of one 

 of their ends. These segments then join in pairs at their free ends to 

 form larger loops (Figs. 11 and 12). This stage is synapsis and re- 

 presents an end to end union (telosynapsis) of univalent (homologous 



