200 Sargant . — Formation of the Sexual Nuclei 
coloured nuclear sap seems to run in between the two rows of 
granules like a soap-film between knitting needles. Thus the 
space between such rows is often more highly coloured than 
the surrounding region, as may be seen to the right of Fig. 6 . 
In that part of the nuclear section it almost seems as if fission 
of the ribbon had not taken place, or was incomplete ; but on 
the left of the figure the sap is clear, and no mistake is 
possible. 
Division of the spirem-ribbon has now taken place in two 
directions. The rows of chromatin-granules which border it 
have been separated from each other by longitudinal fission, 
and the double thread thus formed has been transversely 
divided into lengths. These lengths, each consisting of two 
dotted filaments much twisted on each other, are in fact 
immature chromosomes, and when they have assumed a more 
compact shape, we shall find that there are twelve of them. 
The development of the mature chromosome from each 
pair of twisted filaments begins at once, and it is a curious 
fact that the process is accompanied by all the signs of 
synapsis. I have already spoken of the gradual solution 
of the nucleolus. In Figs. 7 and Ja we see an amorphous 
mass of nucleolar matter which recalls an earlier stage (cf. 
Fig. 3 <2). The twisted threads cluster round this mass at one 
side of the nuclear cavity, and the nuclear membrane becomes 
obscure or actually disappears. The contraction itself is 
clearer at a rather later stage than that shown in Fig. 7 a, and 
is never so well marked as in the embryo-sac nucleus 
(I, Fig. 18), but its character cannot be mistaken. In 
examining anther-sections under a low power, I have fre- 
quently been unable to decide whether the contracted nuclei 
at one end of the loculus were younger or older than those in 
the spirem-stage at the other end. Indeed, it requires fairly 
high magnification, and some attention, to distinguish between 
stages of synapsis which are just passing into the spirem- 
condition and the contracted stages which follow it. 
It should be noticed that in the stage represented in Fig. 7 a, 
the presence of coloured sap between the dotted filaments is 
