318 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, published 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 bv 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 notably in this country, established 
under the Carnegie Institution, a station for experimental 
