388 Edmund B. Wilson. 



outlines can only with difficulty be made out, and then only after 

 long extraction. In stage c (early post-synapsis) they again 

 spread through the nuclear cavity, giving the appearance of an 

 interrupted, contorted and more or less confused spireme, com- 

 posed of delicate and somewhat varicose threads (Fig. 6/>). In 

 stage d (Fig. 6c) the threads become somewhat shorter and thicker 

 and have a more open arrangement, but still show a very marked 

 spireme-like arrangement. I believe the threads to be at this 

 period longitudinally split, though this can only be made out with 

 difficulty. This stage is well characterized by the condition of the 

 large idiochromosome, as described beyond, and by the appear- 

 ance of a pale plasmosome. In stage e the threads become mark- 

 edly shorter and thicker, ragged in outlines, often faintly show a 

 longitudinal split, and diminish somewhat in staining-capacity. 

 The chromosomes now undergo a great change, becoming in 

 stage / very loose in texture, showing only vague boundaries, and 

 almost completely losing their staining-capacity, so that it is 

 difficult to represent their appearance in a black and white figure 

 (Fig. 6^). As may be seen from the figure the chromosomes 

 now give the appearance of a rather vague, pale, finely granular 

 network, in which traces of a spireme-like arrangement can 

 usually be seen, but they cannot be clearly made out as individual 

 bodies. Stage g again shows a great change (Fig. 60) the chro- 

 mosomes having resumed their staining capacit)^ and definite 

 boundaries, and now appearing as long, coarse, winding threads, 

 often showing rather ragged outlines and a more or less distinct 

 longitudinal split, as in stage e; the two stages may, however, at 

 once be distinguished both by the position of the cells in the testis 

 and by the different relation of the plasmosome and the chromo- 

 some-nucleoli, as described below. The condensation ot the 

 chromosomes now takes place, the succeeding three stages follow- 

 ing in rapid succession. In stage h the long split rods shorten 

 and thicken, stain much more deeply, and assume a great variety 

 of forms — curved double rods, dumb-bell shaped figures (some- 

 times longitudinally split), closed rings, and peculiar cross-forms. 

 (Fig. 6p, q, which show all the chromosomes from a single 

 nucleus.) In stage i (early prophase) all these forms condense 

 into quadripartite tetrads or dyad-like bodies, the latter consisting 

 of two symmetrical halves closely joined together and frequently 

 showing no trace of a second division, though in the same nucleus 



