8 CONTENTS 



CHAPTER III 



PAGE 



THE BASIS OP THE POPULATION PROBLEM: (2) THE 



QUALITATIVE ASPECT 64 



(1) In the chromatin of the nucleus we have apparently to recognize 

 the physical basis of the inherited qualities which (2) take the form 

 of predispositions towards the development of certain characters. 

 (3) Difference between modifications and mutations. (4) ' Pure Line ' 

 and (5) Mendelian investigations indicate nature and behaviour of 

 latter on crossing. (6) Germinal change consists in the apparent 

 addition, dropping out, or modification of ' factors ', the causes of 

 which (7) are unknown, and are not due to the inheritance of acquired 

 characters. (8) Owing to the death-rate being selective, different 

 germinal constitutions are differently favoured, and thus (9) per- 

 manent change among species in a state of nature comes about. 



CHAPTER IV 



THE POPULATION PROBLEM AMONG MEN .... 80 



(1) The population problem among men has, owing to the evolution 

 of reason, assumed in both aspects a wholly different form. (2) To 

 follow the nature, causes, and results of these changes a sketch is 

 required of human evolution — especially of social evolution. History 

 only provides a partial record for a few thousand years, and (3) we 

 are thus dependent for social liistory upon our knowledge of primitive 

 races which may be applied to prehistoric races. (4) Outline of 

 future chapters. 



CHAPTER V 



HUMAN FECUNDITY 88 



(1) We have to ask whether human fecundity has changed and 

 what the effect of certain customs is upon fecundity. (2) It is not 

 to factors influencing the male (3) but to factors influencing the • 

 female that we have to look. (4) The length of the mature period 

 increases with good conditions ; (5) the interval between births has 

 decreased in mankind, (6) while the number at a birth has probably 

 increased (7) owing to good conditions. (8) That human fecundity 

 has increased is supported by other evidence, (9) including the 

 number of children, and (10) was held by Darwin and others. (11) 

 Polygamy has had no influence, but lactation, age at marriage, early 

 intercourse, and development of fat adversely affect fecundity. 

 (12) Calculations of possible increase. 



