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W. E. HOY, JR. 



STAGE II. 

 Shortening of the Elongate Embryo, xy type. 



2x Type. 



Diabrotica vittata. 



Miss Stevens ('08) reports 21 chromosomes "of various sizes 

 and shapes" in the spermatogonia of this species. Her figure 

 shows one large macrochromosome pair. If arranged in a paired 

 series graded in size, the unpaired x-chromosome would appar- 

 ently be placed about ninth, followed by two pairs of smaller 

 chromosomes. In the first maturation division the #-chromo- 

 some moves undivided to one pole of the spindle, giving them two 

 classes of secondary spermatocytes. Of the resulting spermato- 

 zoa, one half contain an x-chromosome, and one half do not. 



The second maturation of the egg was reported in a paper 

 preliminary to this (Hoy, '14). Eleven chromosomes enter the 

 female pronucleus. Fig. 12 shows the chromosomes of the first 

 maturation division. There are eleven, each of them appearing 



