VARIATION AND HEREDITY 115 



of the original fertilized ovum. Thus the 

 parent is rather the trustee of the germ- 

 plasm than the producer of the child. In 

 a new sense the child is "a chip of the old 

 block." The clarifying and corroboration of 

 this doctrine of germinal continuity has 

 been one of the most important steps of 

 post-Darwinian biology. It enables us to 

 understand why like tends to beget like; 

 and it also suggests, what is hardly less im- 

 portant, that the new departures or varia- 

 tions, which we have spoken of as individual, 

 are really expressions of the changeful vitality 

 of the undying germ-plasm. As Bergson 

 puts it: "Life is like a current passing from 

 germ to germ through the medium of a 

 developed organism. . . . The essential thing 

 is the continuous progress indefinitely pur- 

 sued, an invisible progress, on which each 

 visible organism rides during the short 

 interval of time given it to live." 



Organic Changes Analyzed. — Great 

 progress has been made in recent years in 

 studying the individual peculiarities of plants 

 and animals, in registering their amount 

 and their frequency. The collection and 

 analysis of these "biometric" data are of 

 fundamental importance, for the Darwinian 

 method of interpretation is like that of 

 Lyell, throwing the light of the present on 



