CONTENTS. 



PAGE. 



PART I. INTRODUCTORY 5 



Mendel's law of segregation 5 



Linkage and chromosomes 5 



Crossing-over 7 



The Y chromosome and non-disjunction 8 



Mutation in Drosophila ampelophila 10 



Multiple allelomorphs 1 1 



Sex-linked lethals and the sex ratio 14 



Influence of the environment on the realization of two sex-linked characters 16 



Sexual polymorphism 17 



Fertility and sterility in the mutants 18 



Balanced inviability 19 



How the factors are located in the chromosomes 20 



The sex-linked factors of Drosophila 21 



Map of chromosome X 22 



Nomenclature 24 



PART II. NEW DATA 25 



White 25 



Rudimentary 25 



Miniature 26 



Vermilion 27 



Yellow 27 



Abnormal abdomen 27 



Eosin 28 



Bifid 28 



Linkage of bifid with yellow, with white, and with vermilion 29 



Linkage of cherry, bifid, and vermilion 30 



Reduplicated legs 31 



Lethal 1 31 



Lethal la 32 



Spot 33 



Sable 34 



Linkage of yellow and sable 35 



Linkage of cherry and sable 37 



Linkage of eosin, vermilion, and sable 37 



Linkage of miniature and sable., 40 



Linkage of vermilion, sable, and .bar 40 



Dot 44 



Linkage of vermilion and dot 44 



Bow 46 



Bow by arc 47 



Lemon body-color 48 



Linkage of cherry, lemon, and vermilion 48 



Lethal 2 49 



Cherry 51 



A system of quadruple allelomorphs 51 



Linkage of cherry and vermilion 51 



Compounds of cherry 52 



Fused 53 



Linkage of eosin and fused 54 



Linkage of vermilion, bar, and fused 56 



