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 nomial 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 inay 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 known. 



Fundamentally, entirely independent of chromosome synapsis 

 and segregation are the phenomena of dominance and reccssive- 

 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 froin 

 one heredity set or combination to another. Dominance and 

 recessiveness should come under possible control like latency and 

 activity. Doininance and recessiveness when compared to activ- 

 ity and latency of factors do not decidedly indicate jjresence and 

 absence. From the standjjoint 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 



