134 The Spermatogenesis of Desmognathus Fiisca 



PLATES III AND IV. 



The figures of tlhcse two plates must he reduced y^ more {i.e., y^ off any diameter) 

 to permit of correctly comparing size with figures on the first two plates. 



Division of Spermatocyte II. 



The following- figures may be compared with the corresponding stages 

 of the Spermatocyte I: 



Fig. 19. Secondary Spermatocyte. Two danghter-cells of the first di- 

 vision at the " dispirem " stage. The chromosomes have expanded some- 

 what; the apices of the V's are still toward the pole of the cells. 



Fig. 20. Secondary Spermatocj^te. Later stage. Slightly oblique view 

 showing five of the chromosomes, which are seen to be double. They 

 still maintain their polar arrangement. 



Fig. 21. Secondarj^ Spermatocyte. Polar view of a similar stage. Eight 

 chromosomes more or less complete are shown. The polar arrangement 

 is still maintained. 



Fig. 22. Secondary Spermatocyte. Ti'ansection (equatorial section) of 

 the nucleus at a deeper level. The cut chromosome threads are shown; 

 and their arrangement in fours is indicated. The apex of one group of 

 four threads is seen. 



Fig. 23. Secondary Spermatocyte. Later stage. Three cells are shown; 

 in one the section is near the middle and the chromosomes, now short- 

 ened to X's, are seen to lie superficially. In the other tw^o cells, the sec- 

 tion cuts the nucleus nearer the s\:rface. 



Fig. 24. Secondary Spermatocyte. Stage similar to that shown in 

 Fig. 23. Crosses and X's are shown. 



Fig. 25. Secondary Spermatocyte. Longisection at the beginning of 

 spindle formation. The chromosomes are in the form of crosses and are 

 next the nuclear membrane. 



Fig. 26. Secondary Spermatocyte. A later (?) stage. The nucleus is 

 cut superficially. One centrosome only can be seen next the cell mem- 

 brane. 



Fig. 27. Secondary Spermatocyte. Spindle formation. The one centro- 

 some is located near the cell-membrane, the other at a distance, near 

 the nucleus, and a spindle is not yet formed between them. 



Fig. 28. Secondary Spermatocyte. Later stage; spindle almost com- 

 pleted. Nuclear membrane has been dissolved. 



Fig. 29. Group of five secondary spermatocytes. The equatorial plate 

 stage just being established. The crosses in most cases have been dis- 

 solved, and the daughter-Vs have become applied to each other. Tw^o of 

 the cells are cut somewhat obliquelj' so that only one pole of the spindle 

 is shown. 



Fig. 30. Secondary Spermatocyte Typical equatorial plate stage. The 

 spindle is quite spherical; mantle fibers are shown. 



Fig. 31. Secondary Spermatocyte. Anaphase. Daughter-Vs passing to 

 the poles of the spindle. 



