3i8 BIOLOGY AND ITS MAKERS 



on Pangenesis, in which he departed from that theory as 

 developed by Darwin. The observations upon which he 

 based his conclusions were made upon the transfusion of 

 blood in rabbits and their after-breeding. He studied the 

 inheritance of stature, and other characteristics, in human 

 families, and the inheritance of spots on the coat of certain 

 hounds, and was led to formulate a law of ancestral inher- 

 itance which received its clearest expression in his book, 

 Natural Inheritance, pubHshed in 1889. 



He undertook to determine the proportion of heritage 

 that is, on the average, contributed by each parent, grand- 

 parent, etc., and arrived at the following conclusions: ''The 

 parents together contribute one-half the total heritage, the 

 four grandparents together one-fourth, the eight great-grand- 

 parents one- sixteenth, and all the remainder of the ancestry 

 one-sixteenth." 



Carl Pearson has investigated this law of ancestral inher- 

 itance. He substantiates the law in its principle, but modifies 

 slightly the mathematical expression of it. 



This field of research, which involves measurements and 

 mathematics and the handling of large bodies of statistics, 

 has been considerably cultivated, so that there is in existence 

 in England a journal devoted exclusively to biometrics, which 

 is edited by Carl Pearson, and is entitled Biometrika. 



The whole subject of heredity is undergoing a thorough 

 revision. What seems to be most needed at the present time 

 is more exact experimentation, carried through several gen- 

 erations, together with more searching investigations into 

 the microscopical constitution of egg and sperm, and close 

 analysis of just what takes place during fertilization and the 

 early stages of the development of the individual. Experi- 

 ments are being conducted on an extended scale in endowed 

 institutions. There is notablv in this countrv, established 

 under the Carnegie Institution, a station for experimental 



