The Germ Cells of Aphis. 33^ 



Fig. 25. First polar body (/)') containing five chromosomes, and second polar spindle. Two chro- 

 mosomes appear in two sections h and c, and a part of one belonging to the first polar body is seen in 

 section a. 



Fig. 26. First polar body (/>'); chromosomes of second polar body (/>"); and female pronucleus 

 forming (n). 



Fig. 27. Male and female pronuclei. The arrows indicate the path of the sperm nucleus. 



Plate IV. 



Fig. 28. Resting spermatogonium of Aphis oenothorae. 



Fig. 29. Spermatogonia preparing for mitosis, showing both nucleolus and chromosomes. 



Fig. 30. Spermatogonium showing 9 of the 10 chromosomes, and no nucleolus. 



Fig. 31. Equatorial plate of spermatogonial mitosis. 



Fig. 32. Spermatocyte of first order in resting stage. 



Fig. 33. Spermatocytes of first order, showing {a) eight of the ten chromosomes not paired and 

 (fc, c, d) chromosomes, of the same size in pairs. 



Fig. 34. Spermatocytes before division, possibly a "synapsis'' stage. 



Fig. 35. Equatorial plate of first maturation mitosis, showing variations in arrangement of chromo- 

 somes (a, b, c), and double chromosomes, (c) chromosomes lettered as in Figs. 7, 12 and 23. 



Fig. 36. Side view and oblique view of equatorial plate of first maturation mitosis showing double 

 chromosomes. 



Fig. 37. Anaphase of first maturation mitosis showing "lagging'' chromosome. 



Fig. 38. Later stage of the same. 



Fig. 39. A pair of spermatocytes of the second order in a partial resting stage, the lagging chromo- 

 somes still connected. 



Fig. 40. Equatorial plate of second maturation mitosis, chromosomes lettered as in Figs. 7, 12, 

 23 and 35. 



Fig. 41. Anaphase of second maturation mitosis. 



Fig. 42. Spermatids in various stages. 



