CHAPTER XIV 

 THE FOUNDATIONS OF GENETICS 



The transmission of definite characters from parents to offspring 

 is an obvious phenomenon, but it was not until early in the 

 twentieth century that scientific knowledge of the subject was 

 sufficient to be regarded as a division of science. Under the name 

 genetics, coined by the English scientist, Bateson, it has since 

 taken its place among the important biological sciences. 



Genetics deals with the origin of individuals, and in this is 

 closely connected with embryology. They differ in that the latter 

 science is concerned solely with the gradual differentiation of a 

 complete individual from the germ cells, while genetics attempts 

 to explain the appearance in every individual of the characters 

 previously found in its progenitors, and to account for the differ- 

 ences which occur. The correlation of these two fields of study is 

 a problem whose solution will be very valuable to biology. 



Heredity and Adaptation. The facts of adaptation considered 

 in the last chapter are too orderly for explanation on any other 

 basis than that of correlation of the organism and its environment. 

 Correlation involving change in any factor cannot fail to bring 

 about different results, which in the organism would necessitate 

 modification of structure and function. In order to affect a species, 

 these modifications must not only affect individuals belonging to 

 it, but must reappear generation after generation. The constancy 

 of the species, such as it is, must be preserved, and yet somewhere 

 in the succession of generations change must be introduced if 

 evolution is a reality. 



It is the difficult task of genetics to unravel this paradoxical 

 situation and to determine the limits of permanence of hereditary 

 characters. Fortunately there has been no lack of available 

 material. Although working hypotheses still constitute a large 

 part of the fabric of evolution and genetics, they are supported 

 by an ever increasing mass of facts. Evolutionary change has 

 not yet been ])rought under control so that it can be produced in 

 the laboratory, but more and more evidences of its existence 



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