2/6 ELIZABETH A. SMITH. 



1. The nucleus has increased slightly in size and there is a 

 corresponding increase in chromatin material, which is arranged 

 into large, deeply staining, irregular masses. That the cell 

 remains with the chromatin in the diffuse condition into which it 

 passed at the end of the spermatogonial division for only a short 

 time seems evident from the fact that few cells are found in 

 that stage. Correspondingly large numbers contain the deeply 

 staining masses. These masses are entirely different in appear- 

 ance from those formed at the end of the multiplication period 

 by the fraying out of the univalent, spermatogonial autosomes; 

 they are larger, more irregular and stain more deeply. Their 

 formation is not clear, the nucleolus separates into the chromatin 

 particles which were loosely incorporated into it; the granules 

 in the faintly staining network aggregate into clumps and the 

 chromatin while increasing in bulk, develops a greater capacity 

 for staining. Part of the process is a reversal of the behavior 

 at the end of the spermatogonial division. These masses are so 

 closely crowded that the number cannot be counted with cer- 

 tainty, but it is about equal to the diploid number. Most of 

 them have ragged, irregular edges (Figs. 18, 19 and 20). One, 

 marked X, stands out distinctly on account of its round, smooth 

 outline and this later becomes the sex-chromosome. Toward 

 the close of the stage, slender threads begin to extend out between 

 the masses. 



2. Leptotene Stage. Each mass formed in the preceding stage 

 ultimately becomes converted into a slender thread through the 

 gradual outward migration of its component granules (Figs. 21, 

 22). The conditions correspond to that found by Montgomery 

 ('n) in Euchistus, and by the Schriners ('06, a and &) in Tomop- 

 teris, Spinax and Myxine. The whole nucleus is now filled with 

 fine, granular, much interlaced threads and it is impossible to 

 determine their number. It may be that each mass only forms 

 one thread, in which case there would be 24 threads which 

 corresponds with the diploid number minus one. 



The sex chromosome (Fig. 23) can be distinguished by its 

 more compact make-up and more regular outline. It retains its 

 shape and staining capacity, after the nucleus is filled with 

 threads. 



