Chromosomes in Pollen Mo they -cells. 
335 
with a look of amusement thus : 1 Do you think Flemming has made 
a mistake in the salamander? ’ referring to that author’s classic paper on the 
speratogenesis in Salamandra. No, we did not believe that Flemming 
could have been wrong in the matter in question, and the most eminent 
cytologists at the time, including the master under whom the writer worked, 
could not think of a reducing division occurring except in the second 
or homotypic mitosis. As regards the observers who in recent years have 
interpreted the first mitosis as a reducing division, holding that the chromo- 
somes separate crosswise and not along the line of the longitudinal split, it 
may be said without doing any injustice to the ability of these workers, 
that the evidence set forth by them has not been wholly convincing. 
The establishment of the fact that the segments of the heterotype 
chromosomes (the daughter chromosomes) are split lengthwise during the 
anaphase, together with a more accurate knowledge of their subsequent 
behaviour in the reconstruction of the daughter nuclei and during the 
homotype mitosis, precluded all possibility of a reduction division in this 
mitosis in so far as the higher seed plants are concerned. Furthermore, 
the Mendelian principle of segregation of characters in certain hybrids 
seemed to demand a reducing division, and whether this principle be correct 
or not, it has certainly accomplished much good in stimulating a search for 
a reducing and a qualitative mitosis. Botanists, therefore, directed their 
renewed attention to the first mitosis with present results. Although Farmer 
and Moore were probably the first to present the most convincing series of 
facts in behalf of the reduction in number taking place in the first or hetero- 
typic mitosis, yet the credit for this explanation belongs by right of priority 
to Heuser for the higher plants and probably to Korschelt for animals. 
The belief in the individuality of the chromosomes is now almost, 
if not quite, universal among cytologists and students of heredity. A con- 
sideration of this doctrine in the light of the rapidly increasing data, and the 
very general agreement among the various observers concerning the manner 
in which the reduction in number of the chromosomes is accomplished, 
brings the investigator face to face with very important and far-reaching 
problems. Among these the question of the recognition of the identity of 
the chromosomes in the resting nucleus has received attention by recent 
workers, and the result has been the suggestion of the prochromosome idea. 
In certain plants there is a tendency of the chromatin to form lumps 
or masses in the resting condition, in which there is often a general 
uniformity in size, and when the number of such lumps approaches the 
number of somatic chromosomes, each mass has been looked upon by 
some as representing a prochromosome, or the centre of organization of 
a chromosome (Rosenberg, ’04 ; Overton, ’05). In the light of the facts 
presented in this paper, it is evident that the plants here considered lend no 
support to such a view. The chromatin does not always appear in the 
