74 



EDMUND B. WILSON 



EXPLANATION OF TEXT FIGURES 



Figures 1 to 9 are from camera drawings, and are not schematized except 

 that in a few instances the chromosomes have been artificially spread out in a 

 series in order to facilitate comparison. Figs. 2 k-l are somewhat more enlarged 

 than the others. In all the figures d denotes the double chromosome or 'd-chro- 

 mosome,' s the small chromosome, X the large idiochromosome and Y the small. 



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Fig. 1 The second spermatocyte-division in Nezara viridula. a-d, metaphases 

 in side view; e-g, anaphases; h, i, polar views of two sister-groups, middle ana- 

 phase, from the same spindle and in the same section. 



tion, appears in several other pentatomids (e.g., in Euschistus, Coe- 

 nus and Mineus). But Nezara forms no exception to the rule that 

 the central chromosome is the idiochromosome-bivalent. In N. 

 viridula this is immediately apparent in side views (often also in 

 polar views) where the central chromosome is seen to consist of two 

 very unequal components, the smaller being not more than one 

 fourth or one fifth the size of the larger (fig. 1 a-c). In the ana- 

 phases these separate and pass to opposite poles, while all the others 

 divide equally (fig. 1 e-g). Polar views of middle or rather late 

 anaphases, when both daughter-groups can be seen superposed 

 in the same section, clearly show the marked difference of the 

 two groups in respect to the idiochromosomes (fig. 1 h-i). All the 

 facts are here so nearly similar to those seen in Euschistus or 

 Lygaeus as to require no further description. 



