CHAPTER VI

THE   CORRESPONDENCE   BETWEEN   THE

DISTRIBUTION OF THE CHROMOSOMES

AND OF THE GENETIC FACTORS

Attention has been called to the fact that paired
factors are distributed in the same way as are
homologous chromosomes, and that factors which
are assorted independently are distributed in the
same way as non-homologous chromosomes. In
proof of the latter point there is Wilson's evidence
for a Metapodius with three homologous m-chromo-
somes. It was found that the extra m goes to the
gamete that receives X as often as to the other
gamete, Miss Carothers describes a somewhat
similar case in certain grasshoppers, in which the
distribution of a pair of unequal chromosomes is
independent of the distribution of the X chromo-
some. Not only are the pairs of factors assorted
independently, as are the chromosomes, but in
Drosophila, where the number of independently
assorting groups of factors has been determined, it
has been found that the number is identical with the
number of chromosome pairs. Moreover, even the
relative sizes of the groups—both as determined by
the number of factors they contain and by the fre-
quency of crossing over within them—are the same

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