640 Fraser . — The Behaviour of the Chromatin in 
arisen is probably due to the fact that the very severance of cross con- 
nexions which tends to obscure the split, makes possible the approximation 
of the first strands of the now free spireme, and the consequent pulling 
apart and rearrangement by which fresh attractions come into play, and new 
pairs are produced. 
Where a presynaptic association of paternal and maternal segments 
occurs, evidence of its existence must be looked for, not in the double 
thread, but rather in the pairs of chromosomes of similar form which have 
been recorded by Muller (8, 9 ) for the sporophyte of Yucca and other 
plants, and by Reed ( 10 ) for that of Allium. Pairing of this type has not 
been recognized in Vicia. 
Summary. 
1. The spore mother-cell shows a dense, finely granular cytoplasm, 
and a large nucleus. The nuclear reticulum is spread just inside the 
membrane, and shows an irregularly diamond-shaped mesh such as is 
found, both in other diploid, and in haploid nuclei (PI. XLIII, Fig. 1). 
2. The first indication that reduction is about to take place, consists in 
the separation of the reticulum from the nuclear membrane (Fig. 2). The 
membrane enlarges and a considerable contraction of the chromatin mass, 
occurs. During synapsis the chromatin retains its reticulate character 
(Fig- 3 )- 
3. In the loosening of synapsis some of the cross connexions of the 
reticulum break down (Fig. 4), and free lengths of spireme appear (Figs. 5-8). 
Some of these form pairs of similar loops, and other paired figures between 
the sides of which approximation takes place (Figs. 5-9). 
4. The loosened spireme extends throughout the nuclear vacuole ; 
in its threads the longitudinal fission, initiated in the preceding telophase, 
and recognizable in the diamond-shaped mesh of the reticulum, can still be 
traced (Figs. 10, 11). 
5. Pairing between independent portions of the spireme becomes more 
frequent, and the rearrangement entailed pulls the thread into a loose knot 
(Fig. 12). 
6 . The thread becomes shorter and thicker, and the second contraction 
figure is produced (Figs. 13, 14). 
7. The spireme breaks up into seven paired segments, the gemini 
(PI. XLIV, Figs. 16, 17), which are thus produced by the association of 
different parts of the spireme. It is indifferent whether this association takes 
place laterally (PI. XLIII, Figs. 7, 12) or end to end (Figs. 6, 8, 14). 
8. The nuclear membrane disappears, the cytoplasm invades the nuclear 
area, forming the spindle, the gemini shorten and thicken, and are arranged 
on the equatorial plate (PI. XLIV, Fig. 18). 
