STUDIES ON CHROMOSOMES. 257 



FIG. 19. Primary spermatocyte of Langshan fowl. See comment under 17. 



FIG. 20. Ditto. The curved element lies close against the other chromosomes 

 in the equatorial plate stage and if the preparation were not greatly decolorized 

 would be indistinguishable. 



FIG. 21. The curved element in a spermatocyte of a Rhode Island Red fowl. 

 X 1,200. 



FIG. 22. Primary spermatocyte of Plymouth Rock fowl, side view of meta- 

 phase showing the curved chromosome lying just above the equatoiial plate. 



FIG. 23. Primary spermatocyte of Langshan fowl, the curved element seen 

 tangentially and therefore foreshortened; easily seen to be the typical element 

 when focus can be shifted. 



FIG. 24. From Plymouth Rock fowl. See 18 for comment. 



FIG. 25. From Langshan fowl. See 17 for comment. X 1,300. 



FIG. 26. Ditto. X 1,300. 



FIGS. 27, 28, 29. Showing various relations of the special chromosome to the 

 spindle in primary spermatocytes. 



FIG. 30. Polar view of metaphase in a Plymouth Rock fowl, the curved ele- 

 ment lying at the upper edge. 



FIGS. 31, 32. Ditto in Langshan and Rhode Island Red fowls respectively. 



FIG. 33. Anaphase of a dividing primary spermatocyte in the Plymouth 

 Rock fowl. The curved chromosome has passed over undivided to one pole. 



FIGS. 34, 35. Stages somewhat similar to that shown in 33. In 34 the division 

 has proceeded further; the cytoplasm is constricting to complete the division and 

 the chromosomes are undergoing their second pairing, the group to the right hav- 

 ing already formed a 4-group. 



