The individuality of the chromosomes and their serial arrangement, etc. 125 
telophases they appear in contact with the nuclear membrane as soon 
as it is formed and as the nucleus enlarges they move out with the mem- 
brane. Düring early synapsis there is an indication of the attachment 
of the leptoneme spirem to the membrane, and in diakinesis the paired 
chromosomes again appear at the periphery of the nucleus. This be- 
havior seems to indicate that there is some sort of organic Connection 
between the chromosomes and the nuclear membrane. 
The paired chromosomes are in some way carried toward the center 
of the nucleus. The serial arrangement still persists and the chromo- 
somes of a pair become so closely pressed together that there are few 
which clearly show evidence of their double nature. That they are double 
is perfectly evident from their number as well as from a study of the 
stages immediately preceding and following. Such a condition is shown 
in figure 26. The behavior of the bivalent discrete spirem is entirely 
similar to that of the single discrete spirem in the prophases of the soniatic 
divisions (compare figs. 25 and 26 with 10 and 11). 
As the nuclear membrane breaks down, the f ihres extend into the 
nuclear cavity and the bivalent spirem becomes flattened into the plane 
of the equatorial plate. Neither here nor in the somatic divisions is there 
such a shrinkage of the nuclear membrane upon the mass of chromosomes 
as Lawson (1911 b) maintains is to be found in Disporum, Gladiolus, 
Yucca, Hedera, and Alliuni. 
In a polar view of this stage the whole spirem is in view. The two 
chromosomes of a pair can be identified when they lie in a profile \’iew. 
This is the position in which many are found during the early stages of 
the heterotypic equatorial plate. Figure 27 shows this stage ; in this figure 
there are thirty-seven masses of chromatin nearly all of which unmistake- 
ably consist of paired chromosomes. It is possible that at least two of the 
masses may consist of individual chromosomes which have either never 
paired or have already separated. It is interesting to note that at this 
stage one pair of chromosomes appears slightly larger than the rest. 
No heteromorphic chromosomes have been observed at any previous 
stage, yet in the polar view of the equatorial plate of the reduction divi- 
sion this larger pair seems to appear quite constantly. The difference 
is shght and the halves of the pair are apparently separated in the divi- 
sion as are the others. 
The serial arrangement of the paired chromosomes is also strongly 
suggested at this stage. When the distance between adjacent pairs in 
different parts of the series becomes less than that between successive 
pairs, it is often difficult to trace the spirem with certainty. Usually 
