CHAPTER XVII 

 GENES AND CHARACTERS 



What Is Inherited? The resemblance of successive generations 

 leads us to say that certain characters are inherited. For all 

 practical purposes this is true and sufficiently accurate. We do 

 receive from our parents the character in question to the extent 

 that in ourselves the character develops from material received 

 from the preceding generation and perfected during ontogeny. 

 A more accurate analysis shows that the thing actually handed 

 down from one generation to the next is some constituent of the 

 germinal chromosomes which is capable of bringing about the 

 development in the new generation of the same character which 

 its progenitors had developed in the old. That some such entity 

 exists for every unit character is evident from the facts already 

 cited. The determiner in general is called a factor; the material 

 entities within the chromosomes are called genes. 



What Are Genes? During the stages of cell reproduction 

 when the chromosomes are evident as distinct bodies they are 

 more or less compact. At other periods the chromatin is obvi- 

 ously granular, made up of particles called chromomeres. Thus far 

 the cell has refused to yield up other secrets of chromatin structure 

 to the cytologist, and the gene remains a theoretical, not to say 

 hypothetical, unit. Like the molecules, atoms, and electrons of 

 modern physics and chemistry, genes lend themselves admirably 

 to the explanation of phenomena of inheritance, and in the logical 

 results obtained on this basis lies the justification for the use of 

 the term. 



Genes may l)e defined as chromatin units occupj'ing definite 

 parts of the chromosomes. Their function is to bring to expression 

 in the developing organism the unit characters for which they 

 stand, and to give rise to other similar genes which shall con- 

 stitute the link with the next generation. 



Somatoplasm and Germplasm. This distinction between 

 genes and the characters resulting from their presence in the body 

 emphasizes a distinction which has attained great importance in 



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