THE ENERGY OF EVOLUTION. 493 



an occasion of the same or similar irritations is offered, 

 a reaction takes place as formerly in the parental or- 

 ganism, of which it was then a part and whose desti- 

 nies influenced it." In explanation of this theory, 

 Hering says : "We notice, further on, that the process 

 of development of the germs which are destined to 

 attain an independent existence, exercises a powerful 

 reaction both on the conscious and unconscious life of 

 the whole organism. And this is a hint that the organ of 

 germination is in closer and more momentous relation 

 to the other parts, especially to the nervous system, 

 than any other organ. In an inverse ratio, the conscious 

 destinies of the whole organism, it is most probable, 

 find a stronger echo in the germinal vesicles thari else- 

 where." 



If heredity is a form of memory, its laws may re- 

 semble those of the psychic memory. In the latter, 

 everything depends on what we call the strength of 

 the impression. A single impression is often easily 

 forgotten, and the certainty of recollection is largely 

 dependent on the frequency of repetition of the stimu- 

 lus. This is the essence of mental education, and it 

 is probably the law of education of the germ-plasma 

 as well. Thus may be understood how stimuli end- 

 lessly repeated through long geologic ages, must pro- 

 duce results far more profound and lasting than spo- 

 radic impressions of modern and artificial origin. 



It must be here remarked for the benefit of the 

 reader who may be unfamiliar with the explanation of 

 the psychic memory, that it is the conscious part of 

 memory which gives it its psychic character. This 

 side is due to a fundamental molecular arrangement 

 caused by stimuli, which may be retained for long 

 periods without expression in consciousness. Thus 



