Cardiff: Synapsis and reduction 287 



39-44 were made convinces me that these parallel threads are in 

 process of conjugation and not in process of fission as undoubtedly 

 most investigators formerly and many at the present time have 

 interpreted their parallel arrangement. Compare, for instance, 

 figures 39 and 40 with figures 43 and 44. There can be no question 

 in regard to the age of the two, judging merely from the extra- 

 nuclear structures, as the character of the cytoplasm, the round- 

 ing -off of the cell-walls, and also the degree of development of 

 the other organs of their respective flowers. Then there is the 

 great difference in size in the nuclei themselves, as shown by the 

 figures, which were made by careful camera drawings. While 

 there is some slight variation in size of the nuclei in the various 

 plants there is a very evident gradual increase in size from the 

 time the mother-cell is formed up to synapsis. In the earlier 

 stages (figures 39 and 40) the chromatin is for the most part near 

 the nuclear wall and it is difficult to represent it all in a drawing, 

 therefore these two figures are sectional views of the nuclei. At 

 these stages the parts of a pair are much farther from each other 

 than in the later stages (figures 43 and 44). In stages shown by 

 figures 43 and 44 the threads have for the most part left the 

 nuclear wall and are becoming massed in the nuclear cavity. 

 They are very close together, in many places actually in close 

 contact so as to appear but one thread, while in other places only 

 the chromomeres are in contact. Where the threads are actually 

 in contact no differentiation of the thread into linin and chromatin 

 is possible ; the whole thread appearing to be composed of a con- 

 tinuous mass of chromatin as in the threads in the postsynaptic 

 stages. The bivalent character of the threads disappears entirely 

 in synapsis (figure 45) except at times where a portion of a thread 

 can be seen on the side of a synaptic knot, when this bivalent 

 character can be made out. 



Often synaptic knots like the one in figure 46 can be found 

 with portions of threads projecting from the chromatin mass # 

 These invariably show a bivalent character. Figure 46 is proba- 

 bly of a nucleus just coming out of synapsis. Later stages of 

 the thread, disentangling from the knot (figures 47 and 48), show 

 clearly the bivalent character. The univalent parts of these biva- 

 lents undoubtedly represent the threads seen in presynaptic stages. 



