x CONTENTS 



PAGE 



Multimodal curves 48 



Correlation and the correlation coefficient 49 



Regression 55 



Employment and value of the statistical method 56 



CHAPTER IV 

 THE PHYSICAL BASIS OF HEREDITY 



Introductory 57 



Heredity a consequence of the genetic continuity of cells 57 



The chromosomes 57 



Somatic cell division 59 



The production of germ cells 60 



Synapsis its significance 63 



Independent distribution of chromosomes 63 



Number of chromosome combinations 65 



Chromosomes and sex in Drosophila 65 



Recapitulation of the mechanism of heredity 67 



CHAPTER V 

 INDEPENDENT MENDELIAN INHERITANCE 



Introductory 68 



Mendelism essentially statistical 68 



Mendel and his discovery 68 



The monohybrid 68 



Mendelian terminology 71 



The chromosome interpretation in a monohybrid 73 



Sex-linked inheritance 74 



The mathematical adequacy of Mendelism 77 



Thedihybrid 81 



A case in maize ' 81 



The chromosome interpretation ; 33 



Mathematical consideration 83 



A case in guinea pigs 85 



A case in Drosophila 87 



Thetrihybrid 90 



A case in snapdragons 90 



Multi-factor hybrids 94 



Four-fold factor segregation in mice 94 



Methods of dealing with genetic data 95 



Validity of segregation ratios 100 



CHAPTER VI 

 LINKAGE RELATIONS IN MENDELISM 



Introductory 104 



Chromosome numbers and factors 104 



