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Allen . — Nuclear Division in the 
appearance of the short, fine threads, and show a tendency to an elongation 
in the direction of the connecting fibres. These fibres also become more 
uniform in thickness. All these changes are in the direction of the forma- 
tion of a spirem ; but, as may be seen from Fig. 8, the whole structure 
is still plainly a reticulum. At this stage there appears not infrequently 
a pairing of the fibres, due to the fact that two fibres, sometimes short, 
sometimes of a length equal to half the diameter of the nucleus, run close 
together and approximately parallel, terminating at either end in the same 
knot. Instances of this sort appear in Fig. 8, and a particularly good 
illustration in Fig. 9. Cases of paired fibres at this stage, however, are 
hardly numerous enough to attract special attention, except in view of 
subsequent events. 
The nuclear membrane, which in the earlier stages has appeared 
in section as a deeply blue-stained line, is now much less easily distinguish- 
able, though it can always be followed. The difference in appearance 
seems to be due to some change which takes place at this stage that affects 
the affinity of the membrane for stains. The nucleus in its growth has 
become in general longer in one diameter, whereas in previous stages 
it was nearly or quite spherical. It is sometimes located toward one side of 
the cell, but its position is still usually central. 
Synapsis. 
The transformation of the reticulum into a spirem goes on rapidly. 
The fibres increase in length, tending more and more toward a uniform 
thickness ; the whole intra-nuclear system is now (Fig. 10) seen to be 
composed of rather slender blue-staining fibres or strands, still interrupted 
in many places by red-staining bodies of irregular size and shape. It 
appears as though the material of the knots were being drawn out along 
certain of the fibres of the former reticulum, and in the process were 
assuming the staining properties of the fibres. Cases of the pairing of the 
fibres now become gradually more frequent, due, apparently, to an ap- 
proximation of the individual strands during or after their formation from 
the knots ; and at the same time there appears a tendency toward a heaping 
up or aggregation of the nuclear materials, a tendency which is first 
noticeable in occasional nuclei at a stage similar to that shown in Fig. 8. 
The density of this aggregation, which is the beginning of the synapsis 
stage, increases (Figs. 10, 11, 12), about in proportion as the pairing of the 
fibres becomes more frequent ; and it is impossible to avoid the impression 
that the heaping up of the whole system is closely related to the ap- 
proximation of the fibres in pairs. Almost simultaneously with the first 
occurrence of the aggregated condition (Fig. 10), the greater part of the 
nucleolar material appears as one or more masses flattened against the 
