234 CHARLES W. METZ 



diploid nuclei are given in figures 78 to 80. They differ in no 

 essential respect from those in Calliphora and Musca. 



Likewise the other Muscidae studied (Muscina stabulans, 

 Calliphora viridescens, Lucilia sericata, and Pseudopyrellia 

 sp.) agree with those already described. 



Sarcophagidae 



Sarcophaga (figs. 81-97). Several species of Sarcophaga 

 have been used in this study and have been found to agree so 

 completely in respect to chromosome behavior that they will 

 be treated as a whole. For specific references see explanation 

 of figures on p. 270. Haploid groups from second spermato- 

 cyte divisions are given in figures 81 and 82, and from first 

 spermatocyte divisions in figures 83 and 84. The last named 

 is a side view showing the inequality of the X Y chromosomes at 

 the time when they separate during reduction. Corresponding 

 diploid groups are represented by figures 85-88 (spermatogonial), 

 figure 89 (ovarian follicle cell) and 90 (somatic, embryonic cell). 

 In the male groups (figs. 85-88) the difference between X 

 and Y (smallest chromosomes) is plainly evident. Prophases 

 showing the early appearance of the pairs, and quite comparable 

 with those in the Muscidae, are given in figures 91 (somatic, 

 two sections of same nucleus), and 92 to 94 (somatic). An 

 anaphase from a similar cell (embryonic glandular tissue) is 

 given in figure 95. It clearly shows the persistence of the paired 

 association and indicates the relative positions occupied by 

 chromosomes when they enter the telophase and subsequent 

 resting stage. In this figure the spindle fibers are schematized, 

 but the chromosomes as in other figures are drawn in their 

 exact position. Figures 96 and 97 are taken from multiple 

 groups (somatic) showing respectively 24 and 48 chromosomes. 

 The former is significant because it shows tetrad aggregates 

 instead of pairs (compare with figs. 85-90 and see pp. 252 and 

 253). In the latter the chromosomes are so massed together 

 as to obliterate the associations. 



