14 15 16 



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

 1-8. Oogenesis of Phyllaphts. 

 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. IT. Equal division of the larger secondary spermatocyte. 

 1 2- 1 6. Polar divisions of eggs of Phylloxera fallax. 

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



producing egg. 



