Sex Dclcrminaliou 



i8 = 



In this connection it will be worth while to consider brielly 

 some of the work of Bridges (5), which provides the "final" 

 demonstration that the chromosomes are the bearers of hereditary 

 characters, and that the sex chromosomes are really the effective 







Fig. 29. — Shaded X chromosomes carries gene (V) for red eye; 

 unshaded X chromosome lacks this gene (i.e., condition v)] V chromo- 

 some of male distinguished by shape. Individuals carrying l' are 

 red eyed; those lacking it are vermilion eyed. This diagram shows how 

 vermilion female (upper left) mated with red male (upper right) results 

 in red daughters (lower left) and vermilion sons (lower right). 



units in determining sex. Occasional non-disjunction of the A' 

 chromosome during gametogcnesis in a vermilion female results in 

 the production of two abnormal types of eggs. (t'A') (rA') and O 

 (fig. 30). The matings of these two abnormal types of eggs with 



