648 Beer. — Studies in Spore Development. III. 
account. It depends upon the degree to which the chromosome substance 
becomes diffused whether a coarse or a fine network results. 
Soon after the new nuclear membranes have developed round the 
daughter nuclei, and therefore at an early stage of the telophase, one 
or more nucleoli can be observed lying among the chromatin contents 
(Figs. 10, 11). 
First Meiotic Division. 
At the conclusion of the last premeiotic division the nucleus passes 
into a complete condition of rest indistinguishable from that separating one 
premeiotic division from another. Such a nucleus I have already illustrated 
in Fig. 1. At the commencement of meiosis there is a small but distinct 
growth in size of the nuclei, the average nuclear diameter of the resting 
cell being 14/x, whilst that of the nuclei shortly before synapsis is 17/x. 
During this growth many of the anastomoses of the chromatic reticulum 
become withdrawn, so that the close network of the resting nucleus is con- 
verted into a much looser one with wider meshes (Fig. 12). The nucleoli 
still remain in about the same number (usually from three to eight), and 
with the same appearance, as in the resting nuclei. 
The next step in the progress of meiosis is the contraction of the 
chromatin network. In Fig. 13 we see that this contraction has com- 
menced on one side of the nucleus, whilst in Fig. 1 5 the synaptic contraction 
has been completed. The nucleoli, which not infrequently appear vacuolated 
at this period, are partly enclosed among the contracted meshes of the 
chromatin reticulum, whilst others may lie free from the tangle. 
During synapsis the chromatin network becomes finally transformed 
into an unbranched spireme free from all anastomotic connexions. This is 
already clear at the stage represented in Fig. 17 a, in which the coil of 
chromatin is becoming loosened and redistributed through the nuclear 
cavity. Another fact is apparent in the same drawing, and this is the clear 
demonstration of the existence of a longitudinal split in the filaments which 
are uncoiling. The short length of spireme depicted in Fig. 17 b shows 
this particularly well. 
Gradually the spireme, free from all cross connexions or anastomoses, 
unfolds entirely and winds freely through the nuclear cavity (Figs. 18, 19). 
The longitudinal division of the threads, which could be clearly seen as the 
synaptic tangle loosened, is usually again lost sight of when the spireme 
has completely developed. As a rule the filaments are smooth, slender, 
and homogeneous in appearance. Occasionally, when the differentiation of 
the stain has been brought to a particular point, the appearance of lighter 
and darker coloured areas, corresponding to a differentiation of linin and 
chromatin, can be seen, but usually the thread is stained uniformly. There 
is a good deal of difference between the arrangement of the coils of the 
