334 Mottier . — The Development of the Heterotypic 
that his Figs. 3-5 may be convincing, it is necessary to show the relation of 
such pieces as Figs. 3 a, 3 b, 3 c, and 4 a, 4 b, and 4 c to a large part of the 
remaining thread in their respective nuclei. Berghs seems to have assumed 
that the sister threads divaricate, that they do not become closely applied 
again in the spirem, and that those which form loops and so forth unite at 
one end after cross segmentation. I am convinced that Overton (’ 05 ), 
Miyake (’ 05 ), and Allen (’ 05 ) have been led into similar errors. If there 
should be any question concerning this point in Lilium , there can be 
no doubt in the case of Podophyllum, that the bivalent chromosomes are 
produced by an approximation of two chromosomes arranged end-to-end 
in the spirem, and even as regards Lilium the observed facts seem to admit 
of no other interpretation. 
That the first mitosis in the pollen mother-cells is the reducing division 
was first asserted by Heuser in 1884 for Tradescantia virginica , and ten 
years later by Korschelt (’ 95 ) for an animal, Ophryotrocha puerilis , one 
of the annelids. Speaking of the • chromosomes when arranged in the 
equatorial plate of the first mitosis in the pollen mother-cell, Heuser says : 
‘ Hier sind in der Stern form die Elemente aussergewohnlich lang, — sie 
reichen fast von Pol zu Pol. Ihre eigentliche Theilung wird nicht durch 
Langsspaltung, sondern durch eine nochmalige Quertheilung in der Nahe 
des A equators besorgt ; dann erst, also nach Anlage der Tochterkerne, 
erfolgt die Langsspaltung der Tochterstrahlen.’ 
From this it is evident that Heuser regarded the first, or heterotypic 
mitosis, as a reducing division, and that the separation of the chromosomes 
was a cross segmentation and not a separation along the line of longitudinal 
fission. He was the first also to state that the daughter segments were 
split lengthwise as they passed to the poles. Heuser gave no figures 
of Tradescantia in the paper cited, and his conclusions were regarded 
as a mere guess, and consequently little heeded by subsequent observers. 
The same may be said of Korschelt ’s account of Ophryotrocha , although, 
judged in the light of what is now known for many animals, he seems 
to have made out a tolerably clear case. As regards certain worms, how- 
ever, the results of F'oot and Strobell (’ 05 ) seem to leave no doubt as to the 
correctness of this view. Even admitting that Heuser’s conclusion was 
largely in the nature of a guess, and there have been many since 1884, it 
was, nevertheless, based upon certain correctly observed, though insufficient, 
data. To show the influence upon investigators of conclusions drawn by 
eminent specialists from a series of apparently correctly observed and well- 
organized facts, the writer takes the liberty to recall an incident that 
occurred when he began the study of mitosis. In 1896, while working 
in a foreign laboratory, he remarked to a fellow student that, if there 
was any such thing as a reducing division in higher plants, the same takes 
place during the first mitosis in the pollen mother-cells. His friend replied 
