May, 1915.] 
The Chromosome Mechanisvi. 
5i7 
has one allosome and the female two, the highest efficiency char¬ 
acter may appear to be transmitted only thru the male simply be¬ 
cause the female cannot get the double dose of favorable allosomes 
except from a male. It is probable also that there are sex-limited 
characters whose factors are not in the allosome. In such cases 
the male of female condition modifies the activity of the factor. 
Besides the segregating results due to normal cell divisions there 
is, of course, the possibility of irregular segregations and the fusion 
of parts of one chromosome with another. Irregularities in re¬ 
duction and vegetative karyokineses may thus produce funda¬ 
mental changes in heredity. Irregularities may be of three gen¬ 
eral types. 
a. The chromosomes may be doubled from the previous 
number of the species, probably thru failure of a reduction 
division. 
b. Increase or decrease of the usual number may be brought 
about by some of the chromosomes being left behind on the 
spindle, or by the entire synaptic pair or the daughter halves 
being pulled to one pole 
c. Material from one chromosome may possibly be trans¬ 
ferred to another when fused ends of two univalents are pulled 
apart in the reduction metakinesis and material belonging to one 
chromosome might also be detached and drawn into another 
during the protochromosome stage of reduction. 
The question of the origin of an hereditary factor in a chromo¬ 
some or the absolute loss of a factor involves a consideration of 
the mechanism, and the chemical, physical and vital properties 
of the chromosomes about which we know little or nothing at the 
present time. But that the chromosome itself is a mechanism 
apparently as complex in its own way as the nucleus itself is 
revealed by the microscope even with present methods. What 
further complications may exist until the larger chemical units 
are reached can only be conjectured. There is also a possibility 
that the mosaic arrangement of the chromosomes in the zygote 
may influence the expression of hereditary factors and the arrange¬ 
ment and adjustment of chromatin granules and any other struc¬ 
tures present in the linin plasm may have something to do with 
the peculiar hereditary properties or abilities manifested by living 
matter. 
