382 KATHARINE FOOT. 



PLATE I. 



FIGS, i, 2, 3, 4. First spermatocyte rest stages, each showing a distinct centro- 

 some in varying proximity to the nucleus. No cell membranes are differentiated. 



FIG. 5. First spermatocyte nucleus showing a single nucleolus and the chroma- 

 tin segregating to form the chromosomes. 



FIG. 6. Two first spermatocyte nuclei with granular chromatin segregating to 

 form the chromosomes. The nucleolus has disappeared. 



FIG. 7. Numerous first spermatocyte nuclei showing successive stages of the 

 differentiation of the chromatin. In the earlier stages the chromatin is apparently 

 homogeneous and later it is granular and segregating into definite masses to form 

 the chromosomes. A few centrosomes are differentiated. 



FIG. 8. Numerous first spermatocyte nuclei showing later stages than those 

 of Fig. 7. In many of the nuclei the chromatin has segregated into 5 distinct 

 masses foreshadowing the 5 bivalent chromosomes of the first spermatocyte meta- 

 phase. 



FIG. g. First spermatocyte nuclei about the same stage of development as 

 those of Fig. 7. 



FIGS. 10, ii, 12 and 13. Each figure shows the 5 bivalent chromosomes of the 

 first metaphase. In each figure one or more of the chromosomes is a dyad, fore- 

 shadowing the first division. An unequal bivalent, which is typical of so many 

 Hemiptera, is clearly shown in each group. 



FIG. 13. All the chromosomes of this first metaphase group are dyads, fore- 

 shadowing the division of each. The large and small chromosomes of the unequal 

 bivalent are detached and each is a dyad. This indicates that each will divide in 

 the first division and that therefore the resulting halves will undoubtedly separate 

 in the second division in the manner typical of so many Hemiptera. 



FIG. 14. Late anaphase of the second division. The chromosomes are too 

 small and too closely segregated to determine their number and form. 



FIG. 15. Three telophases of the second division. Each shows an unequal 

 division of the chromatin, this being the sole evidence, at this stage, of the separa- 

 tion of the large and small moieties of the unequal bivalent. 



FIG. 16. On the left a photomicrograph of a small group of chromosome-like 

 structures from an immature ovary. From these the yolk-spheres are developed. 

 X 450. On the right a sketch of a group of chromosomes from an embryo in an 

 egg at the basal end of the ovary. 



FIGS. 17, 18. Two germinal vesicles from young ovarian eggs. In Fig. 17 the 

 chromatin has partly segregated into threads, and a single nucleolus is present. 

 Fig. 18 shows numerous small dense nucleoli, and the separate chromatin threads 

 suggest a progressive step in the forming of the chromosomes though their abnormal 

 number may be due in part to the technique. 



