Neo-Mendelism 91 



characters with the following statement: "This is an 

 example of a feature which is probably very wide- 1 

 spread in the plant world, but of which at present we 

 know little." Long before any further important work 

 was done along this line in the plant world, however, 

 MORGAN (2) published the results of his very careful 

 and intensive breeding experiments with the fruit fly. 

 His ideas have had a very profound influence upon 

 subsequent work in genetics. He has given us a more, 

 accurate picture of the hereditary mechanism and one 

 that fits the facts better than any previously proposed. 

 In simplest terms the picture is this. Each chromosome 

 is a rodlike structure and numerous determiners are 

 arranged in a line along this rod. 



We cannot discuss here the many ways in which this 

 fundamental conception has cast light upon work in 

 genetics. Suffice it to say that it has resulted in a 

 new " school" of geneticists whose experiments have 

 been more intensive, more exact, and perhaps more 

 " fundamental" than those of any other school. The 

 work so far has been done mainly with the fruit fly 

 and is of a rather complicated nature. We will present 

 here some of the simplest underlying ideas merely to 

 show the nature of MORGAN'S hereditary mechanism. 

 It will be seen how such a mechanism may explain such 

 phenomena as the coupled and antagonistic characters 

 in corn. This general situation, however, will now be 

 referred to by the term linkage, which is in more com- 

 mon use. 



When first considering Mendel's law the statement 

 was made that more than one determiner might be 

 located on a given chromosome. As yet we have 



