On Variations in Chromosomes, 
495 
to those shown in figs. B, 6, 27 and 37, were not fonnd so fre- 
-quently as the others. No two chromosomes were ever fonnd to be 
exactly alike. 
It has been suggested that the chromosomes may be the bearers 
of some of the hereditary characters but not of others *). Racial charac- 
ters, that is characters which are fonnd in all the individuals forming 
a race of animals or plants, cannot be borne by individual chromosomes 
becanse the chromosomes are distributed in an alternative manner to 
the gametes before fertilization. If a racial character were represented 
in a chromosome or part of a chromosome, 25% of all the individuals 
in each generation would lack that character, while 25% would have 
it doubled. Tliis does not happen. Individual characters, it is claimed 
nn the other hand, are transmitted in an alternative manner just as the 
chromosomes are distributed to the gametes, and are probably borne by 
individual chromosomes or parts of chromosomes. The characters which 
are transmitted according to the law of Mendel are claimed as individual 
characters. In the great majori ty of Mendelian experiments domesti- 
cated animals or plants have been dealt with, and characters which have 
been the subjects of the experiments have been simply individual varia- 
tions or characters exaggerated by man’s selection. Man has at the 
same time always selected variability. The few cases of Mendelian 
experiments with natural races seem to show that local variants 
give Mendelian results while geographically separated races of the 
same species when crossed show biending of the characters in which 
they differ * 2 ). 
If the chromosomes are the bearers of individual variations as I 
have suggested, then the establishment of the fact that chromosomes 
vary constantly in form and size takes us one step fnrther towards the 
origin of variations. The mingling of different chromosomes in fertili- 
zation ( Amphimixis ) may prodnce new combinations of already existing 
characters in the off-spring; it cannot possibly produce new variations. 
Montgomery says, with regard to his observations referred to above, 
“Such variations in the behaviour of germ cell chromosomes might well 
be the basis of congenital variations. And a form such as Euchistus, 
that exhibits chromosomal Variation in a fairly large percentage of cases, 
*) C. E. Walker, “Hereditary Characters and tlieir Modes of Transmission”. 
Edward Arnold, London. 1910. 
2 ) Prout and Bacot. Proc Roy. Soc. B. Vol. LXXI. 1909; Entomologist’s 
Record, XV and XVI; Trans. Entomological Soc., London, 1906; Proc. Entomol. 
Soc. Lond., 1907 ; C. E. Walker, op. cit. 1910. 
