512 
The Ohio Naturalist. 
[Vol. XV, No. 7, 
Now we can make the following possible hypotheses in regard 
to heredity: 
1. All the hereditary factors are in the cytoplasm and other 
protoplasmic structures outside of the chromosomes. 
2. Part of the hereditary factors are in the chromosomes 
and part in the protoplasm outside of the chromosomes, especially 
in centrosomes and plastids. 
3. All the hereditary factors are resident in the chromosomes. 
The last hypothesis still seems to explain all known hereditary 
phenomena. It is probable, however, that all protoplasmic 
structures have hereditary factors. Nevertheless, we can safely 
say that all normal Mendelian heredity must have its factors in 
the chromosomes alone. 
Now it may easily be true that certain hereditary factors may 
be resident in all of the chromosomes of a haploid set, and if the 
synaptic haploids also contained the factor, it could not be segre¬ 
gated out in reduction. Fundamental characters may be of this 
nature. A loss of part of the nucleus would not result in a loss 
of essential factors. The factor may be in all but one of the 
haploid set, all but two, etc., and finally in but one chromosome. 
We can conceive that new' trivial or superficial factors commonly 
originate in but one chromosome or in one synaptic pair and that 
later the property might be acquired by other chromosomes of 
the set. If only one chromosome contains the factor, the sim¬ 
plest kind of Mendelian phenomena will result, in breeding distinct 
varities. 
It is self evident that each chromosome and probably each of 
its component organs contains many hereditary abilities or factors. 
If two definite factors, each of which can produce a distinct 
character, are in the same chromosome, the factors and characters 
must be always linked until the chromosome breaks up abnormally 
into new units or individuals. Such, apparently chromosome- 
linked factors are well knovm. 
Fundamentally, entirely independent of chromosome synapsis 
and segregation are the phenomena of dominance and recessive¬ 
ness. These show a similarity to activity and latency of factors 
as observed in the ordinary growth and life cycle. These phenom¬ 
ena have nothing to do with our chromosome hypothesis except 
in so far as dominant and recessive factors may be shifted from 
one heredity set or combination to another. Dominance and 
recessiveness should come under possible control like latency and 
activity. Dominance and recessiveness when compared to activ¬ 
ity and latency of factors do not decidedly indicate presence and 
absence. From the standpoint of the chromosome hypothesis 
a recessive factor may be either an absence or a presence. The 
whole problem of the influences which cause, modify, or prevent 
