The Visible Basis of Heredity 73 



to the cells as they form, in a very erratic 

 manner, and the resulting embryos are highly 

 abnormal, presumably because the hereditary 

 determiners have gone astray. 



The ceUs of any species of animals or plants 

 always contaia a specific and constant number 

 of chromosomes except as noted below. The 

 number may vary greatly in different animals 

 and plants; thus a biologically famous Uttle 

 fruit fly (p. 81) has four, the mosquito, Culex, 

 has six, the rat sixteen, the frog twenty-four, 

 and a white man forty-seven. In radiolarians 

 it is claimed the number is about i ,600. There 

 is a similar wide variation in the number of 

 chromosomes found in plant cells. There is no 

 connection between the number of chromosomes 

 and intimacy of relationship; animals widely 

 separated in the animal kingdom may have the 

 same number; those very closely related may 

 have an unlike number. 



It is very evident that if the egg of an animal 

 contained the regular number of chromosomes 

 and the sperm brought in as many more at time 

 of fertilization, the new animal developed from 



