78 GENETICS 



Drosophila, Individuals are found at times In which one-half 

 of the body, to the middle line, Is of one sex, the other half 

 of the other sex. Such individuals would be produced if, In 

 an egg containing two X's, in the two-cell stage an X were 

 lost from one of the two cells, but not from the other. The 

 half retaining the two X's would remain female, while the 

 other half would become male.^ 



Loss of a chromosome in the process of cell division has 

 been observed In certain cases. One of the chromosomes be- 

 comes entangled with the advancing cell wall, as the cell 

 divides; It Is thus removed from the cell. If this happened to 

 the X-chromosome In one cell of the two-cell stage In 

 Drosophila, a gynandromorph would be produced. 



Sometimes Individuals are found In which three-fourths 

 of the body Is female, while one-fourth is male; or in other 

 cases nearly the whole body Is female, while a very little is 

 male. Such conditions would arise If one X-chromosome 

 were lost from a cell at a later stage of development. 



Gynandromorphs might also be produced if by some 

 means the X-chromosome of certain cells containing but one 

 X could be caused to divide, while the other chromosomes 

 remained undivided. There are no cases known In which 

 this appears to be the method of action. Gynandromorphs oc- 

 cur In birds as well as In Insects, but are not known In mam- 

 mals. 



3. Changes In the chemical processes occurring In the 

 cell. — We know that the chromosomes affect sex by Influenc- 

 ing the chemical processes in the cells. Any agent that in- 

 fluenced these chemical processes, in the same or a reverse 

 way, would determine which sex would be produced. As 

 before seen, it would be necessary only to alter the balance 

 of the chemical processes occurring. An agent that In Dro- 

 sophila reinforced the action of the autosomes would turn 

 the development In the direction of producing a male. An 



