CHAPTER XII 



SOMATOGENESIS 

 1. THE HEREDITARY TUNNED 



The earlier studies in heredity were concerned with 

 the comparison of successive individuals, or somato- 

 plasms. This phenotypic method has attained a con- 

 siderable degree of success through the analysis afforded 

 by Mendelism. 



A different and still more recent method of attack 

 upon the problem of heredity deals not with individuals 

 but with chromosomes which are generally acknowledged 

 to be the living springs from which flow the streams 

 of inheritance. Such an intensive cytological study 

 of the germplasm has revealed a mechanism that ex- 

 plains to a marvelous extent the results of the experi- 

 mental breeder. 



The demonstration of the parallel between the be- 

 havior of the germplasm as seen in the chromosomes 

 and the performance of the somatoplasm as exhibited 

 in the end results of experimental breeding, is one of 

 the most impressive scientific achievements of our times. 



There is an undoubted causal connection between 

 the genotype and the phenotype at the extremes of the 

 hereditary pageant but between these extremes, that is, 

 between the fertilized egg and the adult, investigators 

 are as yet by no means as confident or well-informed. 



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