86 EVOLUTION AND MAN S PLACE IN NATURE 



environment, as external and lying open to obser 

 vation, greatly aids research, whereas the laws of 

 heredity belong essentially to those processes of 

 germinal growth which Nature has concealed. Never 

 theless, it is certain that the same course of investi 

 gation which leads first to admission of variation, leads 

 further to recognition of inheritance. 



In view of the leading question before us, Man s 

 place in Nature, as that must be concerned more 

 particularly with rational power, it is well to mark 

 that our study of heredity is directed, in the first 

 instance at least, upon the laws of organic existence. 

 There is a physical basis on which the laws of heredity 

 operate. Organism presents at the outset the entire 

 field of observation, whatever questions as to mental 

 inheritance may afterwards arise. Structure and 

 functions include the whole area of research, when 

 now we turn to the phenomena of reproduction, as 

 these may explain the origin of individual forms, 

 bearing visible tokens of parentage. 



The physical basis of inheritance is seen in the 

 cell-life, in the germ-plasm, and the germ-cells, or, 

 even lower still, in the physiological unit. When 

 differentiation of organic forms has been somewhat 

 advanced, the physical basis is extended by the 

 blending of male and female elements, after which 

 the growth of the fertilised ovum passes through the 

 several stages of embryonic life. What was hidden 

 in the germ-cell is revealed at birth. The potenti 

 ality of the fertilised ovum is disclosed in the indivi 

 duality of the newly-born life. This gives in outline 

 the range of research, as we proceed to deal with the 

 laws of organic reproduction. Questions as to intel- 



