The Behavior of the Chromosomes as Studied throngh Linkage. 253 



U. Chromosomes and Mondelism. 



Soon after the revival of interest in IVLendel's work, in 1900, it 

 was pointed out by several authors that there is a close parallel bet- 

 ween the behavior of the chromosomes and that of Mendelian genes. 

 BovERi, Cannon, Correns, Guyer, and Sutton all seem to have 

 called attention to this independently and at about the same time. 

 Correns ('02), wiiose paper apix'ared a few months earlier than that of 

 Sutton ('02) did not explain the independent segregation of genes in 

 the manner adopted by Sutton and now generally accepted. Sutton sup- 

 posed that independent genes are borne by members of different chromo- 

 some pairs, and that in the reduction division the chromosome pairs are 

 separated quite at random; so that the ])r()portiou of maternal and paternal 

 chromosomes received by each gamete is a matter of pure chance'). 



Correns and afterward de Vries ('0.3), apparently independently, 

 may have been influenced by the current conception among botanists 

 that the chromosomes are not really separate, but form a continuous 

 thread even in the division stages. These authors supposed the genes 

 to be arranged in a linear series in the chromosomes ; a conception first 

 brought forward by Rotrx ('83) and used by him to explain why the 

 chromosomes are divided while in the form of long thin threads. CORRENS 

 and DE Yries assumed that at some time during the maturation stages 

 there is a chance for interchange between chromosomes. Thus both 

 authors supposed that the chromosomes after maturation are not purely 

 maternal or paternal, but contain a mixture of genes derived from each 

 parent. In this way, they say, we may explain the independent segre- 

 gation of Mendelian allelomorphic pairs. 



It was soon pointed out that in Pisum and in Antirrhinum there 

 are more allelomorphic pairs than the haploid number of chromosomes, 

 and this was used as an argument against Sutton's inteipretation of 

 the chromosome view. Spillman ('08) has justly insisted that, as a 

 matter of fact, it has never been demonstrated that these genes are 

 independent. The writer has recently gone over the literature on Fisum, 

 and can find no good evidence for more than three independent groups 

 of genes there, although at least 16 definite pairs of allelomorphs are 

 reported. As Spillman says, this case cannot be used as an argument 

 against the chromosome view until it be actually proven that there ai'e 



') This relation has actually been demonstrated for certain chromosomes by the 

 work of Wilson (09) on Metapodius and of C.vrothkus ('14) on several Orthoptor:). 



