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Arlow Burdette Stout 
chromosomes ; Clemens Müller (1909) for Yucca aloifolia, Yucca 
Draconis, and Yucca guatemalemis, various sizes of large and small 
chromosomes; Kosenberg (1909a) for Crepis virem, two small, twö 
large, and two Intermediate in size; Tahara (1910) for Crepis japonica, 
sixteen chromosomes of various sizes; Ishikawa (1910) for Ginkgo iilota, 
twelve bivalent chromosomes of which one pair is large. There is also 
a vast literature regarding heteromorphism among chromosomes in ani- 
mals, regarding which adequate summaries have been given by Stevens, 
Wilson, and Montgomery. 
The chromosomes of Carex aquatilis are at tlieii' maximum develop- 
ment small bodies. They certainly are slightly, if at all, larger than 
the so-called chroniomeres appearing in the spirem of the prophases of 
many plants. On tliis point I have inacle comparisons of the chromo- 
somes as they appear in figures 10 and 11 with the spirem appearing 
in the prophases of the onion. The chromosomes in Carex at this stages 
are about 0,5 </ in diameter, while the spirem of the onion is not less than 
0,8 /< in diameter. The diameter of the spherical chromosomes is, there- 
fore, somewhat less than the thickness of the spirem in the onion at 
the time when the latter first shows the longitudinal split. 
As far as I can observe the chromosomes in Carex aquatilis are ho- 
mogeneous bodies. At no time during the somatic dmsions do they 
appear to be niade up of smaller units, “chroniomeres”, or “ids” as parti- 
cularly conceived by Weismann (1892) and Strasburger (1894). On 
this point the appearance of the chromosomes during somatic dmsion 
is most interesting. As already described in detail, the chromosomes 
are at all stages of the prophases spherical or oval bodies. At no time 
is their substance drawn out into a series of “ids” which may be divided 
equally by a longitudinal split. The division of the chromosomes is 
quantitative, but unless the entire chromosome is of uniform composition, 
it is difficult to see how the division can be equational. 
In marked contrast to this constantly compact Organization of the 
chromosomes of the somatic nnclei are the conditions seen in synapsis. 
Here the chromosomes are spun out at great length into a fine thread, 
the folds of which are intricately interlooped together. Out of this a 
continuous pachyneme thread develops and froni this a double series 
of chromosomes is formed. 
Tlie opportunity for the exchange of actual substance between the 
paternal and maternal germ-plasms during such a Union are very great 
and the various possibilities that exist in such a case are well presented 
by Allen (1905). He points out and discusses the following possibilities ; 
