778 Kemp.—On the Question of the Occurrence of 
erfolgen braucht, den Kernen aufgezwungen wird durch den Protoplasten, 
weil dieser normaler Weise nur auf einen Kern zentriert ist.’ 
In explanation of the disappearance of the tetraploid and binuclear 
cells, Strasburger suggested that as these were to be seen after many hours’ 
subsequent growth, some of them must be passed over into the permanent 
tissue ; also, that the amitotic-like forms seen in nuclei distant from the 
root-tip might easily result in complete separation and degeneration of their 
constituents. He gave figures of binuclear cells alternating with others 
containing degenerating masses of chromatin, and concluded that the dis¬ 
appearance of the tetraploid cells was probably due to lack of sufficient 
centripetal force to hold together such an abnormal amount of chromatin as 
they contained ; that consequently their nuclei broke up either at the 
equatorial plate or diaster stage, or while in rest ; and that in this process, 
a certain amount of the chromatin tended to degenerate, and the normal 
number of chromosomes was re-established. 
Unfortunately, however, Strasburger did not obtain the crucial figures, 
according to the nature of which and to their occurrence or non-occurrence 
Nemec’s theory really stands or falls; and as the figures upon which he 
based his criticism of the latter did not represent those described by 
Nemec as heterotypical in character, the matter remained still in dispute. In 
February, 1909, Nemec reaffirmed his statement, and based upon it further 
arguments in support of his view of the non-continuity of the chromosomes 
as individuals, and of the subsidiary role played by them in the matter of 
heredity. In November of the same year, Strasburger, in defining his 
position with regard to the theories of ‘ Pfropfhybriden again noted that 
Nemec’s heterotypical figures did not occur. Finally, as recently as June, 
1910, Nemec once more insisted upon their occurrence. He further sup¬ 
ported his contention with certain results obtained in the lateral roots of 
radicles which had been several times subjected to the action of chloral 
hydrate. In these he stated that there were at first to be seen numerous 
tetraploid cells, but that after a certain time, i. e. in those lateral roots which 
had attained a considerable length, all such cells had disappeared. He main¬ 
tained that their disappearance must result from one of three processes : 
(1) from reduction of the double number of chromosomes and consequent 
re-establishment of the diploid number ; ( 2 ) from the degeneration and 
absorption of the tetraploid ceils ; or (3) from the cessation of their activity 
of division. 
Among other observers who have investigated this problem there are 
great differences of opinion. Woycicki, Haecker, and Schiller, working re¬ 
spectively with the pollen mother-cells of Larix dahurica and Cyclops eggs, 
support Nemec in his view of the nature of heterotype division. They explain 
the supposed reversion to the latter, and also the occurrence of multipolar spin¬ 
dles, as being expressions of an ‘atavistic tendency the re-establishment of 
