32 ETHEL NICHOLSON BROWNE. 



EXPLANATION OF PLATE IV. 



Nonecta insulata. Serial side views of four spindles of first division, as seen 

 in adjacent sections. Figs. 27-29, .4, B, C, three entire spindles each showing 

 13 chromosomes, one small pair free in the center in B, and a compound chromo- 

 some in C (Ma) consisting of the large and the other small chromosome united. 

 Fig. 30, A, B, C, entire spindle showing 14 chromosomes, two small pairs free in 

 the center in B; the two elements of the compound chromosome are separate as 

 M and a in C and B. 



Some of the chromosomes have been displaced on the spindles so as to lie side 

 by side instead of one above another, for the sake of clearness. 



