BRITISH ASSOCIATION. 303 



and plants are formed as pieces of living material split from the body 

 of the parent organisms. Their powers and faculties are fixed in 

 their physiological origin. They are the consequence of a genetic 

 process, and yet it is only lately that this genetic process has become 

 the subject of systematic research and experiment. The curiosity of 

 naturalists has of course always been attracted to such problems ; 

 but that accurate knowlege of genetics is of paramount importance 

 in any attempt to understand the nature of living things has only 

 been realised quite lately even by naturalists, and with casual excep- 

 tions the laity still know nothing of the matter. Historians debate 

 the past of the human species, and statesmen order its present or 

 profess to guide its future as if the animal Man, the unit of their 

 calculations, with his vast diversity of powers, were a homogeneous 

 material, which can be multiplied like shot. 



The reason for this neglect lies in ignorance and misunderstanding 

 of the nature of Variation ; for not until the fact of congenital diver- 

 sity is grasped, with all that it imports, does knowledge of the 

 system of hereditary transmission stand out as a primary necessity 

 in the construction of any theory of Evolution, or any scheme of 

 human polity. 



The first full perception of the significance of variation we owe to 

 Darwin. The present generation of evolutionists realises perhaps 

 more fully than did the scientific world in the last century that the 

 theory of evolution had occupied the thoughts of many and found 

 acceptance with not a few before ever the ' Origin ' appeared. We 

 have come also to the conviction that the principle of Natural Selec- 

 tion cannot have been the chief factor in delimiting the species of 

 animals and plants, such as we now with fuller knowledge see them 

 actually to be. We are even more sceptical as to the validity of that 

 appeal to changes in the conditions of life as direct causes of modi- 

 fication, upon which latterly at all events Darwin laid much emphasis. 

 But that he was the first to provide a body of fact demonstrating 

 the variability of living things, whatever be its causation, can never be 

 questioned. 



There are some older collections of evidence, chiefly the work of 

 the French school, especially of Godron * — and I would mention also 

 the almost forgotten essay of Wollaston f — these, however, are only 

 fragments in comparison. Darwin regarded variability as a property 

 inherent in living things, and eventually we must consider whether 

 this conception is well founded ; but postponing that inquiry for the 

 present, we may declare that with him began a general recognition 

 of variation as a phenomenon widely occurring in Nature. 



If a population consists of members which are not alike but 

 differentiated, how will their characteristics be distributed among 

 their offspring ? This is the problem which the modern student of 

 heredity sets out to investigate. Formerly it was hoped that by the 

 simple inspection of embryological processes the modes of heredity 



* ' De l'Espece et des Baces dans les Etres Organises,' 1859. 

 f ' On the Variation of Species,' 1850. 



