Plate XIII 



14 15 16 



Oogenesis and spermatogenesis in Aphids, after MORGAN (1915). 

 1-8. Oogenesis of Phyllaphis. 

 i. Prophase, 2. Metaphase, of oogonial division, with six chromosomes. 



3, 4, Young parthenogenetic ova with six chromosomes. 5, 6, 7. Syn- 



izesis stages of sexual ova. 8. Young sexual ova after synizesis with three 



double chromosomes. 

 9,10,11. Three stages of spermatogenesis. 9,10. Unequal first spermatocyte 



division. 1 1. Equal division of the larger secondary spermatocyte. 

 12- 1 6. Polar divisions of eggs of Phylloxe ra fallax. 

 12, 13. Anaphase and telophase of the single polar division of the female- 



producing egg. 



14, 15. Anaphase and polar body of male-producing egg. 

 i 6. Polar equatorial plate of sexual egg. 



