34 ETHEL NICHOLSON BROWNE. 



EXPLANATION OF PLATE V. 



Notonecta insulata. Fig. 31, metaphase of first division showing 13 chromo- 

 somes, one small one in the center, the other small one attached to the large one 

 forming the compound chromosome Ma. Figs. 32, 33, metaphase of second 

 division, showing 12 chromosomes, both idiochromosomes showing in the center, 

 Fig. 34, initial anaphase of second division, side view, idiochromosome pair in the 

 center. Fig. 35, the same, but idiochromosomes on different fibers. Fig. 36, 

 A and B, sister anaphase groups of second division, from the same spindle. 



