PLATE 21 



EXPLANATION OF FIGURES 



(C. curtipennis) 

 163 to 183 First spermatocyte. 



163 Early prophase, stage h, parasynapsis still occurring. All chromosomes 

 (nine) are present. To prevent confusion, nos. 2, 4, and lOx have been drawn 

 outside the cell boundary, nos. 2 and 4 being moved out radially; no. lOx is from 

 the nuclear-wall region at + near the figure 6. Distal and proximal ends are 

 indicated by dst. and pi'x. respectively, x' to x*"' are points atwhich spindle fibers 

 become attached; they also indicate the proximal end or region. The numerals 

 5-9, 8-10 and 7-11 indicate the linked chromosomes 5 with 9, 8 with 10, etc. One- 

 half (exconjugant portion) of the 7-11 in the proximal region (x' to x'") is included 

 between the similar parts (x'tox") of the 8-10 chromosomes. The remaining parts 

 of each chromosome are still in parasynapsis. 



164 A slightly later stage. All chromosomes present. The autosome pairs 

 still in parasynapsis. End views show each chromosome spireme to be split in 

 two planes mutually perpendicular. 



165 Stage h, similar to figure 163, also showing the nature of the 7-11 com- 

 pound. At a and b, just outside the nuclear membrane, are drawn cross-sec- 

 tions of this chromosome at the two points opposite a and b. No. 4 lies near lOx, 

 and, as in figures 149, 163, 164, 168, etc., is more condensed than the other autosomes. 



166 Stage h, similar to figure 164, showing the four parts of a first-spermato- 

 cyte chromosome before exconjugation sets in. 



167a and b similar examples. Stage h. 



168 Prophase (stage h) approaching that of figure 150. The three multiples 

 and all other chromosomes present. The proximal regions (x, x) are beginning 

 the exconjugation process. The proximal part of one exconjugation portion of 

 no. 4 is in contact with one end of the sex chromosome. 



169, 170 Show association of one end of the no. 4 pair (still in parasynapsis) 

 with one end of the sex chromosome (10.r). 



320 



