INEQUALITIES IN HOMOLOGOUS CHROMOSOMES ERG 
with the sesqui-valent portion, but I have seen no evidence that 
this occurs. Possibly the sesqui-valent portion has become so 
non-functional that it fails properly to attract the normal No. 1 
chromosome in the synapsis period. 
This explanation is the best I can propose, in the light I now 
have, to account for the origin of this long chromosome. The 
facts are that it is approximately two and one-half times the 
length of a normal No. 1 chromosome, all or most of its parts 
are evidently oriented in one direction, and a constriction near 
the distal end marks off a portion which evidently pairs in 
synapsis in the normal manner with the No. 1 chromosome and 
separates from this chromosome in the normal manner in the 
first maturation division (figs. 12, 13, and B, to B;). 
An essential fact is that we have here cases of an abnormally 
large chromosome, which is constant in size in individuals of 
both sexes. Its relative size is the same in all the dividing germ 
cells found in the male, and likewise in the somatic cells (follicle) 
of the female. I believe that it is a permanent structure, so far 
as these two individual animals are concerned. 
A second important fact is that this abnormally large chromo- 
some alternates with a normal chromosome and it may or may 
not be present in either sex. Theoretically, we may have, 
depending on the presence or absence of this chromosome, 
three sorts of male individuals and three sorts of female individu- 
als; those containing two normal No. 1 chromosomes, those 
containing one normal and one abnormal No. 1 chromosome and 
those containing two abnormal No. 1’s._ I have found the first 
two cases in both sexes. The latter case has not yet been found 
in either sex. We have therefore a basis for a Mendelian ratio. 
The presence of one long and one short chromosome might be 
considered the cell condition of the heterozygote, or hybrid; 
the presence of two short chromosomes or of two long ones would 
give the homozygotes, recessive and dominant, if such relations 
may be imagined in so far as these chromosomes are concerned. 
