658 



COLLEGE ZOOLOGY 



Figure 465. Hugo De Vries (1848-1935), a 

 Dutch botanist who formulated a mutation theory. 

 (From Walter.) 



combination. Although there may be a dif- 

 ference of opinion regarding De Vries' 

 contribution to our understanding of muta- 

 tions, nevertheless, he will always be remem- 

 bered as the first person to publish on the 

 rediscovery of Mendel's laws. 



Thomas Hunt Morgan (1866-1945) (Fig. 

 466) was an American biologist, who, next 

 to Mendel, is the most important name in 

 the history of genetics. He published more 

 than 200 scientific papers and 8 books. Al- 

 though much of his work was in the field 

 of experimental embryology, he is best 

 known for his studies in genetics. He used 

 the fruit fly, Drosophila melanogaster, as an 

 experimental organism. His contributions to 

 the mechanism of heredity won for him the 

 Nobel prize (1933), which carries more 

 distinction than any other scientific honor 

 conferred by man. 



H.J. Mullet (1890- ) (Fig. 467) is 

 another American Nobel prize winner whose 

 scientific recognition came from genetic in- 

 vestigations. He started his studies on the 

 location of genes in chromosomes with 

 Morgan. Later he turned his attention 

 chiefly to the study of the nature and causes 

 of mutations in the genes and chromosomes. 

 He worked out quantitative methods of at- 

 tacking these problems. He showed that 



Figure 466. Thomas Hunt Morgan (1866-1945) . 

 an American biologist who reported the first gene 

 mutation (white eye) in Drosophila. (Picture taken 

 in 1932. Courtesy of I.M. Morgan.) 



Figure 467. H.J. Muller (IbVu- ), a Aobel 



prize-winning American who was first to show that 

 mutations could be artificially induced by means of 

 radiation. (Courtesy of H.J. Muller.) 



