3§7 
and of other related Primula Hybrids. 
Fig. 30. Shows the chromatic swelling where the two univalent chromosomes are still in contact. 
Fig. 31. The univalent sides have diverged and concentrated to form the typical heterotype 
chromosomes. 
Fig. 32. Origin of the quadripolar spindle. 
Fig* 33 * The chromosomes arrange themselves on the equatorial plate. Note the laggard 
chromosome. 
Fig. 34. Polar view of the equatorial plate of the first meiotic division, showing the nine chromo* 
somes. 
PLATE XLII. 
Fig. 35. Chromosomes separating and passing to the poles. 
Fig. 36. Telophase of the first meiotic division. Protoplasmic connexions streaming through 
the cell-walls join spindles of adjacent cells to one another. 
Fig. 37. Late telophase. The chromosomes split longitudinally and their sides are beaded. 
Fig. 38. Resting stage. The skeleton of each chromosome is outlined in beads. 
Fig. 39. Reconstitution of chromosomes. 
Fig. 40. Longitudinally split chromosomes going on to the spindle of the second meiotic 
division. 
Fig. 41. Homotype spindle showing the nine chromosomes. 
Fig. 42. Telophase of second meiotic division. 
Fig. 43. P. verticillata. Pollen mother-cell. Spireme coming out of synapsis; tracts coalesce, 
forming a band-like chromatic mass, the beginning of the second contraction. 
Fig. 44. The mass has increased in size. 
Fig. 45. Second contraction from which radiate irregular loops of spireme. 
Fig. 46. Sorting out of the second contraction. The protruding portions show all stages in 
the association of univalent strands. 
Fig. 47. The chromosomes may come out of second contraction in the form of chains of rings. 
Fig. 48. The chromosomes tend to segregate into two groups. 
Fig. 49. Shows longitudinal fission in the substance of the newly separated, univalent chromo- 
somes. 
Fig. 50. The splitting apart of the univalent chromosomes. 
Fig. 51. Condensation of the univalent chromosomes to form the typical heterotype chromosomes. 
Fig. 52. Polar view of an equatorial plate of the first meiotic division. 
Fig. 53. Interkinesis between the first and second meiotic divisions. 
Fig. 54. P. kewensis (type).. Pollen mother-cell. Hollow spireme, showing the association of 
the sides of the loops. 
Fig. 55. Protrusion of chromatin from a nucleus into the adjacent cell. 
Fig. 56. Arrangement of beaded strands of spireme into squares and parallel lines. 
Fig. 57. Concentration of these associations to form the bivalent segments. 
Fig. 58. Further concentration of univalent strands into ladder-like associations. The strands 
coalesce in places. 
Fig. 59. Splitting apart of the univalent segments of each bivalent combination. 
Fig. 60. Further stage in the splitting apart of the univalent chromosomes, and their subsequent 
thickening. 
Fig. 61. The thickened ring-shaped chromosomes tend to collect together into one or two groups. 
Fig. 62. As they redistribute themselves throughout the nucleus they often appear as chains of 
loops. 
Fig. 63. The opening out of the rings to form the bivalent chromosomes. 
Fig. 64. Typical heterotype chromosomes. 
Fig. 65. Polar view of an equatorial plate of the first meiotic division, showing the nine chromo- 
somes. 
Fig. 66. Separation of the univalent chromosomes on the spindle. 
PLATE XLIII. 
Fig. 67. Tetrad. 
Fig. 68. Pollen-grain apparently normal. 
Fig. 69. Pollen -grain depauperate. 
Fig. 70. Nucellus. Prophase showing eighteen chromosomes. 
