ON TIIK UKLATION liF/rWKKN NUMHKIl OF 

 (MIKOMOSOMKS AND NUMBKIl OK TYPKS, 

 IX LATIIYIWS ESPKOIAI.LY. 



Hy (). WIX(iK. 

 (With Plato V.) 



The iiuiiiIkt of simultaiu'ously and indepondently segregating pairs 

 of factoi-s' in the species investigated by genetic experts has, as we know, 

 never yet been found so high Jis to exceed the haploid chroniosonie rniniber 

 of the s|X'cies. Conseipiently, there is still nothing to subvert the theory 

 that the genes have their morphological equivalent in the chromosomes 

 and that these latter are — or can be — individually dissimilar in a given 

 biotyjx; as regards the genes included. 



It is a (juestion of very gi'eat theoretic importance, whether the 

 simultiineously segregating pairs of factors, not mutually connected, can 

 ever exceed the number of chromosomes in the species concerned, this 

 being, so to speak, a decisive point as regards the value of the entire 

 section of the stud\' of chromosomes related to the science of genetics. 

 If a biotype could be found to exhibit segregation of but a single paii- 

 of fact'Ors in excess of the number indicated by the haploid chiomosome 

 value, then, properly speaking, the theory as to the value of chromosomes 

 as bearers of the genetic, segregating units would collapse at once. The 

 nice agi'eement between reduction division and segregation would thus 

 be irrevocably destroyed. 



At a first glance, it might seem likely that we should be able, in 

 highly varying species, to segregate without great difficulty a gieater 

 number of ty[>es than the chromosome number found for the species 

 permits. We can, however, obtain a surprisingly large number of com- 

 binations even from a (juite small number of chromosomes, and it must 

 also be Ixjrne in mind that the theory of agreement between leduction 

 division and Mendelian segregation would by no means be destroyed 

 even if we did succeed in finding a greater number of indei)endently 

 mendling piiii>> of genes (or pairs of gene-complexes) within a Linnaean 



* By this expression is meant pairs of factors, or groups of pairs, between which the 

 phenomenon of linkjifje is not found. 



