240 WALTER S. SUTTON. 



eration might be expected to duplicate the characters of the 

 parent (if environmental conditions remained unchanged) and 

 little or no variability would be expected as long as partheno- 

 genesis persisted. 



In relation to these problems there is great need of a simul- 

 taneous study of the germ-cell divisions and the variation of peri- 

 odically parthenogenetic forms. 



We have seen reason, in the foregoing considerations, to believe 

 that there is a definite relation between chromosomes and allelo- 

 morphs l or unit characters but we have not before inquired 

 whether an entire chromosome or only a part of one is to be 

 regarded as the basis of a single allelomorph. The answer must 

 unquestionably be in favor of the latter possibility, for otherwise 

 the number of distinct characters possessed by an individual 

 could not exceed the number of chromosomes in the germ-prod- 

 ucts ; which is undoubtedly contrary to fact. We must, there- 

 fore, assume that some chromosomes at least are related to a 

 number of different allelomorphs. If then, the chromosomes 

 permanently retain their individuality, it follows that all the 

 allelomorphs represented by any one chromosome must be 

 inherited together. On the other hand, it is not necessary to 

 assume that all must be apparent in the organism, for here the 

 question of dominance enters and it is not yet known that domi- 

 nance is a function of an entire chromosome. It is conceivable 

 that the chromosome may be divisible into smaller entities (some- 

 what as Weismann assumes), which represent the allelomorphs 

 and may be dominant or recessive independently. In this way 

 the same chromosome might at one time represent both domi- 

 nant and recessive allelomorphs. 



Such a conception infinitely increases the number of possible 

 combinations of characters as actually seen in the individuals and 

 unfortunately at the same time increases the difficulty of determ- 

 ining what characters are inherited together, since usually reces- 

 sive chromatin entities (allelomorphs?) constantly associated in 

 the same chromosome with usually dominant ones would evade 

 detection for generations and then becoming dominant might 

 appear as reversions in a very confusing manner. 



1 Bateson's term. 



