ANTICIPATION AND INTERPRETATION 19 



third, the theories and conjectures as to the nat- 

 ural causes or factors underlying this law or con- 

 stituting it. 



The full conception of the law came very late. 

 Apparently Lamarck was the first to grasp Evo- 

 lution in its infinite modern significance, and to 

 see the analogy between the past history of life 

 and a great widely branching tree, having its 

 roots in the simplest organisms, its shorter 

 branches in the lower, and its longer branches in 

 the higher forms of life. According to this now 

 familiar analogy, the living animals and plants 

 of today are the terminal twigs of great branches 

 which represent the lines of extinct ancestors. 

 These branches united near the trunk with oth- 

 ers, whilst still other branches, with their termi- 

 nal branchlets, have entirely died out in past 

 time. Or, to begin at the roots and trace the his- 

 tory upwards instead of downwards, the lower 

 branches of the tree are comparatively few, and 

 represent the great classes of animals which di- 

 vided and subdivided into orders, sub-orders, 

 families, genera, species, and so on. 



Prior to Lamarck this branching nature of de- 

 scent was only very crudely perceived. This was 

 because Aristotle's general view that the exist- 

 ing forms of life constituted a *scale of ascent' 

 from the polyps to man had been revived in dif- 

 ferent aspects, such as the 'perfection chain' of 



