The Visible Basis of Heredity 8i 



other sex due to the presence of the sex chromo- 

 somes is only one factor in the final outcome, 

 though it is probably the most important. 



Professor Morgan, of Columbia University, 

 who has for many years been conducting experi- 

 ments on inheritance in the fruit fly, Drosophila, 

 finds that the hereditary characters behave as if 

 they were bound together in four groups — one 

 large group, one with very few characters in it, 

 and two that are intermediate. Now Droso- 

 phila has four chromosomes in its cells — one 

 very large one, one quite small, and two of 

 intermediate size. Dr. Morgan thinks that this 

 is more than a coincidence. His work tends to 

 show, not only that a specific character is located 

 in a particular chromosome, but that the de- 

 terminer for the character is located at a par- 

 ticular spot in the chromosome. 



It must be apparent that the hereditary 

 characters of an individual animal or plant are 

 determined at the time of fertilization of the egg 

 from which it comes. If this be so, the common 

 belief that prenatal influences produce heritable 

 characters must evidently be false. Farmers 



