THE BREAKDOWN OI CONTINUITY 



TABLt 27 



SPECIES IN PAEONIA (BARBER 1941. STERN 1946) 



Region 



Europe 



Asia 



N. America 



Mlokosewitchii - 

 (Caucasus) 



daurica 



(Crimea, etc.) 



Clusii 

 (Crete) 



Cambessedesii - 



2 other localized species in 

 Mediterranean 



1 widespread in Ukraine 



Witmanniana and varieties (Cau- 

 casus and Elburz) 

 mascula, banatica (widespread) 



officinalis, mollis and varieties 



(N. Mediterranean) 

 Russi and varieties (Western 



islands of Mediterranean) 

 3 other widespread species 



unrelated to any surviving 



diploids 



japonica 



(Japan) 

 8 other widespread 



diploids 



obomta and varieties (E. Asia) 

 No other tetraploids 



2 diploids 



No tetraploids 



have been inferred in grasshoppers. They likewise give novel 

 configurations at meiosis. When any such new types arise as 

 fragmentation or fusion in heterozygotes there is some loss of 

 fertility through irregularity at meiosis. This will favour the 

 segregation and separation of homozygotes of the two types : so 

 soon, at least, as their genie homozygosity does not conflict too 

 strongly with the hybridity optimum of the species. In other words 

 a chromosome change of fusion or fragmentation may be expected 

 to act, like one of inversion and interchange, as a focus of 

 discontinuity in the species. This expectation is borne out when we 

 discover that in making inferences from changes in chromosome 

 numbers in the larger groups, we are able to apply the rules we 

 derive from what happens to the smaller structural changes within 

 the smaller groups, the races and species. 



In the first place the basis of adaptation of races and species lies 

 in their genes. Changes of structure and number of chromosomes 

 are, as a rule, merely the means of directly or indirectly preventing 

 recombination of these genes. The chromosome discontinuities, 



322 



