282 Cardiff: Synapsis and reduction 



crease in size of the chromatin granules, and also by spreading 

 along the thread. As chromatin increases along the linin thread 

 it is generally impossible to distinguish definitely between linin and 

 chromatin, and the appearance of this and much of the other 

 material used recalls the theory that linin and chromatin are merely 

 different phases of the same substance. Figure 3 shows a still 

 greater increase in chromatin and at several places an approxima- 

 tion of threads in pairs as at a and b. An indication of the same 

 pairing can be seen also at a in figure 2. By the time the stage 

 shown in figure 4 is reached the cell has increased greatly in size 

 and shows a decided rounding-off of the wall. The nucleus shows, 

 proportionately, a greater increase than the cell. The nucleolus, 

 however, does not partake of this increase in growth, or at least 

 to a very limited extent. The cytoplasm has become more reticu- 

 lated in structure ; the chromatin has become more evenly dis- 

 tributed over the thread and there is an evident pairing of threads, 

 which, however, is more marked in a slightly later stage (figure 5). 

 In this figure no less than eight distinct pairs of threads or portions 

 of threads can be made out. Most of these pairs seem to be in con- 

 tact with the nucleolus or very near to it In stages but little later 

 the pairing of threads is still more evident, as shown in figures 6-12. 

 Figures 7— 1 1 are taken from five adjoining cells. Figures 6-12 

 show chromomeres actually in contact in many instances, while the 

 portion of the thread between the chromomeres seems to have 

 changed but little from its condition in much earlier cells where it 

 takes the stain very lightly. Chromomeres in many instances show 

 an actual flowing together, as shown in figure 12, which is slightly 

 enlarged. That this is a pairing and not a split seems certain to one 

 examining the preparations. It is not difficult to be sure of the 

 stage in the development of the mother-cell in Acer, owing to the 

 gradual change that takes place in the cytoplasm, which shows a 

 reticulated nature as the cell gets older, and owing to the gradual 

 increase in the size of the nucleus until near the synapsis stage, and 

 because, also, of the changes that take place in the cell-wall, etc. 

 A gradual approximation of the threads in pairs can be followed 

 until the chromomeres actually begin to blend in stages shown by 

 figure 13, a stage just previous to the close synaptic knot. This 

 appearance of the threads is undoubtedly what the earlier invest!- 



