PLATE 1 



EXPLANATION OF FIGURES 



N. undulata, N. irrorata, N. insulata. X 2000 



1 N. undulata, metaphase of the first division, polar view, showing 14 chro- 

 mosomes, two small ones in the center. 



2 N. undulata, metaphase of the first division, side view, showing linear 

 arrangement of the central pairs. 



3 N. undulata, metaphase of the second division, polar view, showing 13 chro- 

 mosomes, XY in the center. 



4 N. undulata, metaphase of the second division, side view. 



5 A, B N. undulata, sister anaphase groups of the second division, from the 

 same spindle. 



6 N. undulata, spermatogonial groups showing 26 chromosomes. 



7 N. irrorata, metaphase of the first division, polar view, showing 13 chromo- 

 somes, one small one in the center. 



8 N. irrorata, metaphase of the first division, side view. 



9 N. irrorata, metaphase of the second division, polar view, showing 12 chro- 

 mosomes. Both X and Y appear in the center. 



10 N. irrorata, metaphase of the second division, side view. 



11 A, B N. irrorata, sister anaphase groups of the second division from the 

 same spindle. 



12 N. irrorata, spermatogonial group, showing 24 chromosomes. 



13 N. insulata, metaphase of the first division, showing 14 chromosomes, two 

 small ones in the center. 



14 N. insulata, metaphase of the first division, showing 13 chromosomes, one 

 small one in the center. 



15 N. insulata, metaphase of the first division, side view, with two small ones 

 in the center. 



16 N. insulata, metaphase of the first division, side view, with one small one 

 in the center and the large chromosome with a small one attached. 



17 N. insulata, metaphase of the second division, showmg 12 chromosomes. 



18 N. insulata, metaphase of the second division, side view. 



19 A, B N. insulata, sister anaphase groups of the second division, from the 

 same spindle. 



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