CONTENTS. 



PACE. 



Part I. Introductory S 



Mendel's law of segregation 5 



Linkage and chromosomes 5 



Crossing-over 7 



The Y chromosome and non-disjunction ° 



Mutation in Drosophila amfelophila ^° 



Multiple allelomorphs " 



Sex-linked lethals and the sex ratio H 



Influence of the environment on the realization of two sex-linked characters i6 



Sexual polymorphism ^7 



Fertility and sterility in the mutants '° 



Balanced inviability " 



How the factors are located in the chromosomes 20 



The sex-linked factors of Drosophila ^^ 



, Map of chromosome X 



Nomenclature * 



Part II. New data ^5 



White ^5 



Rudimentary \ 



Mmiature 



Vermilion 



Yellow ^7 



Abnormal abdomen ' 



r^ ■ 20 



Losm o 



Bifid •■•.•• ;,; f^ 



Linkage of bifid with yellow, with white, and with vermilion Z9 



Linkage of cherry, bifid, and vermilion 3° 



Reduplicated legs ' 



Lethal 1 ^\ 



Lethal \a 11 



Spot " 



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 + 



Linkage of vermilion, sable, and bar + 



Dot ^ 



Linkage of vermilion and dot ** 



Bow f 



Bow by arc *^ 



Lemon body-color • • *„ 



Linkage of cherry, lemon, and vermilion + 



Lethal 2 *^ 



Cherry ■ 



A system of quadruple allelomorphs •> 



Linkage of cherry and vermilion 5 



Compounds of cherry ^' 



Fused " 



Linkage of eosin and fused ^* 



Linkage of vermilion, bar, and fused 5 



3 



