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Charles E. Allen 
process of contraction (as in Figs. 29 b — d, PI. VI), or whether it is loosen- 
ing preparatory to the arrangement of the chromosomes in the equatorial 
plate ; but from the degree of development which the spindle has reached 
and the absence of a elear region about the chromosomes, I am inclined 
to hold to the latter interpretation. In this figure the total bulk of the 
chromosomes appears considerably greater than is usual at this stage — an 
appearance which may result in part from an arrangement of the chromo- 
somes in this particular case in a somewhat flattened group, and in part 
also, verv probably, from an acci dental swelling of the chromatin during 
fixation. 
The chromosomes, as seen in the equatorial plate, are long, slender 
and bent. When the spindle is viewed laterally (PI. VII, Figs. 35 — 40), 
they almost always appear more or less foreshortened; and a polar view 
(as in Figs. 41 — 48, which were drawn from cells in which everything 
but the chromosomes was deeolorized) gives a better notion of their form. 
The ends of two or more usuallv overlap, a fac-t which throws some diffi- 
culty in the way of an exaet determination of their number; but from a 
good many countings, made at different stages and from different views, 
it seems certain that the number is six. Occasionally, as in Figure 43, 
the chromosomes are so far separated that there can be no question as 
to their number. Six were found by the Leeuwen-Reijnvaans (1907 b) 
in the gametophytes of this species, and this number agrees, according to 
Tischler (1908), witli Arens’ later results. 
I have attempted to determine whether individual chromosomes 
are marked by constant size differences. Apparently the chromosomes 
of any nucleus are not of exactly the same length (Figs. 41 — 48); but 
the differences are so small that, taking into consideration the vary- 
ing positions of the chromosomes and the certainty of foreshortening in 
many cases, I have not been able to reduce to any constant formula such 
size differences as may be present. Certainly there are no such marked 
differences as are described by the Leeuwen-Reijnvaans (1907 b), and 
their figures, showing two long chromosomes, two very short and two 
of medium length in eaeh nucleus, are quite ineorrect for Polytrichum 
juniperinum. 
I have found no case in which a longitudinal split was plainly visible 
before or at the time of the equatorial plate; but the forms of the daughter 
chromosomes in the metaphases and anaphases (Figs. 49 — 53), as well as 
their thickness compared witli that of the mother chromosomes, demon- 
strate that the division of the mother chromosomes has been effected 
in the usual way. 
