170 Digby. — On the Archesporial and 
Fig. 44. Another superficial section of the same stage showing threads running closely 
parallel (S.F.). 
Fig. 45. Early synapsis. Association of the sides of the loops (i. e. of two threads) can be seen 
towards the margins of the knot, especially in the S. It will be seen that the two threads are 
separate for a length and then closely associated (S.F.). 
Fig. 46. Superficial section of a portion of a nucleus in early synapsis, showing striking 
similarity of the approaching threads (H.). 
Fig. 47. Synapsis showing the polarization of the threads as loops towards one side of the 
nucleus, and the association of the threads, i. e. the sides of the loops, in pairs actually taking place. 
This is the consummation of the association of the half univalent spiremes (threads) in pairs to form 
the entire univalent spireme (filament) (S.F.). 
Fig. 48. 0 . regalis. This nucleus in synapsis is at a slightly later stage to that of Fig. 47. 
The association of the threads has become closer, leaving only a vestige of ‘ fission ’ between 
them (A.A.). 
Fig. 49. 0 . palustris var. aurea. The spireme filament is beginning to come out of synapsis. 
The association is completed ; the emerging spireme filament is thick, being the product of the 
coming together of the two halves of univalent spireme, i. e. of two threads. From henceforth the 
spireme filament is of an entire univalent nature. Fission is visible in parts (H.). 
Fig. 50. Superficial section of a nucleus coming out of synapsis. Every portion of the spireme 
filament shows fission and that of a very beaded character, characteristic of Hermann fixation (H.). 
Fig. 51. Early hollow spireme. The spireme filament has come out of synapsis and is dis- 
tributed throughout the nucleus. Fission separates more thread-like sides characteristic of Strong 
Flemming fixation (S.F.). 
Fig. 52. Superficial section of a nucleus in the same stage as Fig. 51, showing the looping of 
the spireme (S.F.). 
Fig- 53- The spireme loops incline to arrange themselves round the nucleolus. In this nucleus 
fission is still evident, whilst in some nuclei in the same sporangium (cf. Fig. 59) it is closed (H.). 
Fig. 54. Figs. 54-8 are studies of the conjunction in pairs of lengths of filament, i. e. of entire 
univalent spiremes, the first indication of the evolution of the heterotype chromosomes. Note in the 
loops pointing S. in Fig. 54 the sides are drawn in towards one another and connected by a fine 
transverse strand. Also the two filaments pointing NW. are connected by fine cross strands (H.). 
Fig- 55* Note the conjunction of the univalent sides of the loop suggestive of a future U-shaped 
chromosome. Fission in the univalent sides, separating the threads, is evident (H.). 
Fig. 56. Shows the conjunction of univalents (i. e. of filaments) prophetic of a future X-shaped 
chromosome (S.F.). 
Figs. 57 and 58 show a looping over and conjunction of univalents forming figures typical or 
heterotype chromosomes. In Fig. 57 only vestiges of fission are to be seen (S.F.). 
PLATE X. 
Fig. 59. This nucleus is from the same sporangium as Fig. 53, but is in a slightly later stage. 
Fission has closed, and there is a marked conjunction of filaments, as seen in the looping over of the 
spireme, and in the S. of the nucleus fine transverse strands join the univalent sides (H.). 
Fig. 60. 0 . palustris var. undulata. The spireme in the N. portion of the nucleus is beginning 
to aggregate preparatory for second contraction. Note the conjoining pair of filaments in the SE. 
attached to the nucleolus. They are separate for a distance except for a fine transverse connexion, 
and then closely conjoined and then again separate. No fission is visible (H.). 
Fig. 61. Note the conjunction of filaments end to end to form a closed ring in the N. of the 
nucleus, and the twisting over of two filaments in the centre of the nucleus (H.). 
Fig. 62. 0 . palustris . The filaments are withdrawing from the nuclear periphery and collecting 
towards the centre in preparation for second contraction. Note the loop to the S. of the nucleus 
showing fission. At this stage the spireme filament has definitely segmented and free ends are to be 
seen (H.). 
Fig. 63. Nucleus preparing to go into second contraction. Note the striking example of con- 
junction in the SW. portion of the nucleus. The filaments are closely conjoined for a length and 
then diverge to form a closed loop. No fission is visible. The apparently thickened spireme of the 
nucleus is due to the strong chromic fixative. Towards the SE. striae are visible in the cytoplasm, 
the first sign of the origin of the spindle fibres (S.C.). 
