CHPTEE IV. 



A NEW THEORY OF HEEEDITY. 



The objection to the hypothesis of pangenesis would be almost 

 entirely removed if it could be simplitied — Statement of a new 

 theory — Heredity is due to the properties of the egg — Each 

 new character has been impressed upon the egg by the trans- 

 mission of gemmules — Tendency to form gemmules is due to 

 the direct action of external conditions — The ovum is the con- 

 servative element — The male cell is the progressive element — 

 This theory has features of resemblance to most of the hy- 

 potheses which have been noticed — It fills most of Mivart's 

 conditions also — It is not necessary to assume that the ovum is 

 as complicated as the adult — There are many race characters 

 which are not congenital — There are many congenital charac- 

 ters which are not hereditary — Direct action of external con- 

 ditions — Our theory stands midway between Darwin's theory 

 of natural selection and Lamarckianism. 



If the hypothesis of pangenesis could be so re- 

 modelled as to demand the transmission of only a few 

 gemmules from the various parts of the body to the re- 

 productive elements, instead of the countless numbers 

 which are demanded by the hypothesis in its original 

 form, we should escape many of the objections which 

 have been urged against it. 



If it can be shown that these few gemmules are not 

 necessarily present at all times and in all parts of the 

 body, but only occasionally and in certain regions, we 

 shall escape the difficulty presented by Galton's experi- 

 ments, and the presumption in favor of the hypothesis 

 will be greatly increased. 



If the theory of heredity, in its new form, agrees with 



