10 



ever-widening scale, of successive processes of analysis and 

 synthesis. In each branch of science, along with our keener 

 and keener perception of differences, we come to perceive 

 more and more recondite relations of agreement." 



I have stated that heredity is a physiological law ; but it 

 is a law within a law, being in a sense the effect of genera- 

 tion. The phenomena of inheritance have not only been 

 observed, but the conditions realized ; and the analysis of 

 these has indicated where we must seek for the laws of 

 which heredity is the manifestation laws which are subject 

 to variation and individuation as other natural laws. Phy- 

 siological heredity must be regarded as a physiological 

 necessity of our being inseparably connected with the great 

 law of reproduction, the process of which, although very 

 imperfectly understood up to a comparatively recent period, 

 has still more recently been brought much more within our 

 comprehension, notwithstanding that our knowledge of its 

 nature and functions is even yet incomplete. The respec- 

 tive characteristics and interdependence of reproduction 

 and nutrition, long recognized, are now more fully mani- 

 fested ; and nutrition has been correctly defined as "a 

 perpetual reproduction." 



This would be the place wherein to discuss the minute 

 details of the reproductive process so far as they are known ; 

 but as this would be beyond the scope of the present work, 

 I can only refer the reader to the many and excellent 

 text-books of physiology and embryology which the progress 

 of science has rendered far in advance of their prede- 

 cessors. 



The generation of life from life is a mystery which science 

 has not, and, perhaps, may never solve a mystery in which 

 many more mysteries are hidden and amongst the latter 



