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dition (Lutz, '12, p. 424), it cannot be assumed with safety that these 
common 15-chromosome Lamarckiana mutants result from the fusion 
of 6- and 9-chromosome gametes, except, possibly, in rare instances, 
for 5-9 distributions of heterotypic chromosomes doubtless occur still 
more rarely than 6-8, and a 9-chromosome cell would be expected to 
unite with a 7- far more frequently than with a 6- and to produce a 
i6-chromosome mutant; yet i6-chromosome offspring of 0. Lamarcki- 
ana X O. Lamarckiana appear to be comparatively rare. 
Gates ('09a, pp. 4-5) has pointed out that, owing to irregularities in 
chromosomal distribution, a germ cell might be formed containing two 
chromosomes of one pair and lacking both representatives of another 
pair. The number of chromosomes would therefore remain constant, 
he states, but such germ-cells would be entirely deficient in a 
particular kind of chromosome. He has further shown ('15a, 
p. 298) that if both members of one pair of chromosomes 
may pass to one pole of the heterotypic spindle, resulting in a 6-8 
distribution of chromosomes, it is conceivable that both members of 
another pair might, on rare occasions, pass to the opposite poles at the 
same time. This would equip each daughter nucleus with 7 chromo- 
somes, but not with the usual combination, a b c d e f g. Let us 
assume that this has occurred during male reduction and that two 
pollen grains bearing a' a'- c' d' e' e' f g\ and two bearing - bb' c'd'e' 
j' ^ chromosomes have been formed. Then should one of these male 
gametes, say of the first type, unite with a regular 7-chromosome female 
gamete, we should expect the 14-chromosome plant resulting to have 
aa'a' b- cc' dd' ee' ff' gg' chromosomes instead of the usual aa' bb' cc' 
dd' ee' ff' gg' combination. Gates and Miss Thomas suggested that 
"the variability of the lata-semilata series may depend upon the fact 
that the extra chromosome belongs to a different pair in different cases," 
and add: ''since there are seven pairs of chromosomes, we should then 
expect seven more or less distinct lata-Vike types," but conclude that 
" there is at present no evidence that the plants having 15 chromosomes 
can be divided in this way." 
If both members of any one of the seven pairs of chromosomes 
were capable of passing to one pole, while both members of any" one 
of the remaining six were capable of passing to the opposite pole 
during male, as well as during female, reduction; if regular and ir- 
regular 7-chromosome male and female gametes were formed capable 
of uniting with each other and producing viable seeds, a large number 
