376 RUTH J. STOCKING. 



EXPLANATION OF PLATE I. 



FIG. i. Flemming; safranin and licht-griin. Spermatogonial metaphase, 20 

 chromosomes. 



FIGS. 20 and b. Ibid. Two views of a spermatogonial telophase. 



FIG. 3. Flemming; safranin and licht-griin. Cross section of contraction 

 stage; a and b, c and d, e and /, g and h, x'and y, pairs of chromosomes in cross 

 section, not yet united; j and k, I and m, o and p, pairs of chromosomes in side 

 view, ready to unite; q and r, tops of short loops formed by the thickening, shortening 

 and thickening of two united chromosomes. 



FIG. 4. Flemming, safranin and licht-griin. A little later stage in the con- 

 traction phase, showing loops. 



FIGS. 5, 6, 7, 8. Flemming, safranin and licht-griin. Formation of large loops. 



FIG. 9. Flemming, iron-hsematoxylin. Large loops beginning to straighten 

 out. 



FIG. 10. Hermann, safranin and licht-grun. Formation of spireme. 



FIG. ii. Hermann, safranin and licht-griin. Showing the ten chromosomes of 

 this stage. 



FIG. 12. Hermann, safranin and licht-grun. Spireme, showing tetrad. 



FIG. 13. Flemming, safranin and licht-griin. Late spireme. 



FIG. 14. Hermann, safranin and licht-griin. Prophase of first spermatocyte 

 division, showing ten bivalent chromosomes, including the unequal pair. 



