308 Wisconsin Academy of Sciences, Arts, and Letters. 
and Calendula, and by Overton (’05, ’09a, ’ll) for several plants, 
has been observed by several other investigators. 1 
The doctrine that the chromosomes are permanent and that the 
parental elements remain separate throughout the life cycle of 
the organism was first suggested by Haecker. The fact that 
chromosomes of different sizes in certain plants are associated in 
pairs, as decribed by Strasburger (’05) for Funkia and Galtonia, 
has been substantiated by the subsequent observations of several 
authors on other plants. The nucleus is, therefore, not only double 
in the sense that it contains two sets of parental chromosomes, 
but these chromosomes are arranged in homologous pairs. 
It seems apparent, therefore, that the duality of somatic nuclei 
is due to the association of the homologous chromosomes in pairs, 
each element of which splits during the prophases, as above de¬ 
scribed, rather than that the duality is due to the splitting of the 
telophasic chromosomes as held by Fraser and Snell (’ll), Lun¬ 
degard (’12a, c), Miss Digby (TO, T9), von Schustow (T3), and 
others. I agree with Sharp (T3) that it is not necessary but 
rather unsafe to rely upon the principle of telophasic splitting 
as a premise for the conclusion that the approximation of thin 
threads in the early heterotypic prophase represents the reassoci¬ 
ation of the halves of a single split chromosome, as is done by 
the authors cited. The arrangement of entire chromosomes in 
pairs and the presence of tetrads in diakinesis, as I have described 
them during meiotic divisions of certain plants, argue against the 
necessity of such an assumption. 
Lundegard (’10a, b, ’12c, T5) has emphasized what he believes 
to be a dual tendency of the caryotin during all stages of nuclear 
activity, which tendency is expressed morphologically, according 
to Lundegard by the appearance of double earyosomes or double 
caryotin threads. Although Lundegard holds that morphological 
duality is the same in both somatic and generative prophases, he 
maintains that the duality signifies a qualitative difference in the 
heterotypic prophases, and says: 
“Es geht jetzt hervor, dass die heterotypische Doppelfaden aus einem 
Paarungsvorgang hervorgegangen sein mussen, denn eine qualitative 
Spaltung ware hochst unwahrscheinlich”. 
According to this view the halves of the heterotypic chromo¬ 
somes are qualitatively different, while in the somatic divisions the 
1 See lists given by Stout (’12), Digby (’14), and De Smet (’14). 
