204 HOLISM AND EVOLUTION chap. 



tory what her silent processes have amounted to through 

 millions of years. 



If we set aside this negative and really irrelevant evidence, 

 and also reject Weismann's extreme doctrine of germinal 

 isolation, we find nothing in theory or fact to preclude us 

 from viewing modifications as having an influence through 

 more or less long biological periods on the germ-cells. On 

 the hypothesis of the ''field" which we have found useful 

 before, we may consider these somatic modifications as in 

 the first instance influencing the field of the germ-cells, 

 and only later and in the course of time becoming incor- 

 porated from the field into the hereditary structure of the 

 germ-cell. 



We come thus in effect to look upon modifications as partly 

 the material from which variations have been formed. 

 Modifications due to constant use or disuse, or to per- 

 manent changes in the conditions of physical environment, 

 influence in the first instance the field of the germ-cell, 

 and are thus the earlier phase of the later hereditary struc- 

 tural variations. In fact we may say that modifications 

 are to variations what variations are to specific characters. 

 Throughout organic Nature we find this grand calculus at 

 work, adding up and conserving whatever in the experience 

 and development of the individual is of survival value to 

 the race, and carrying on this organic summation with a 

 fineness and delicacy surpassing that of any mere mechani- 

 cal calculus. What is not incorporated into the hereditary 

 structure remains conserved in the invisible "field" until 

 it is finally accentuated enough to become so incorporated. 

 Nothing of value is lost — traces and residua of organic 

 reactions, reflexes and tropisms, instincts and intelligence, 

 all are conserved or registered in the field until in the lapse 

 of time they are ready to become part of the physical 

 structure. There is no reason, except our ignorance of the 

 facts, why modifications should not thus to a large extent 

 be the conditions precedent of variations. Only in this way 

 can we explain why the trend of Variation is on the whole 

 in harmony with the experience and the past of animate 



