SCIENCE AS A FACTOR OF HUMAN EXPANSION 495 



covery of the relations between the ovum and the germ-layers 

 which arise from it, and the tissues and cells which compose 

 the fuUy-developed organism, was the next great step accom- 

 phshed by embryological science ; and the discovery of KolUker 

 that the ovum is a simple cell, and that the numerous germinal 

 layers which arise from it by repeated segmentation are the 

 origia of all the cells, and consequently of all the parts of the 

 finished organism, was one of the most fertile of biological 

 discoveries. But it is the work of Darwin which forms the 

 crowning-point of biological research in the nineteenth century. 

 By his theory, as Haeckel has said, he brought all the results 

 of the various biological sciences to a common focus, and thus 

 gave them a harmonious interpretation ; and by his principle 

 of selection, which is what we properly call Darwinism, he dis- 

 covered the direct cause of those transformations of species 

 which Lamarck, Goethe, and Erasmus Darwin had believed 

 in without being able to afiord a scientifi.c justification of 

 them. 



It is on the hues indicated by Darwin that all biological 

 research has been pursued during the last forty-five years, and 

 with signal success. We need only refer to Huxley's contribu- 

 tions to comparative morphology and classification ; to Haeckel's 

 work in similar spheres, and to his important discovery of the 

 biogenetic law ; to Oscar Hertwig's fruitful researches respecting 

 the nature of fertilisation ; to the all-important investigations 

 in the domain of positive psychology, carried out by Wundt, 

 Eibot, Sergi, Bspinas, Fritz Schulze, and others, not omitting 

 Flechsig, whose researches into the anatomy of the cerebral 

 structure of the higher animals constitute one of the most valuable 

 achievements of modem science ; and whose theory of the centres 

 of association, or thought centres, although called in question 

 by Sciamana at the Congress of Psychology held in Kome in 

 1905, nevertheless remains a remarkable contribution to positive 

 psychology. And, in the last twenty years, we have had the 



