114 THE LESSON OF EVOLUTION 



simply a case of retrograde development from disuse. 



The principle has also been applied to explain 

 the reduction of parts of flowers, but without any 

 attempt to shew why the reduced part should have 

 been the one to suffer. Plants furnish their 

 growing tissues with nutrient material in a per- 

 fectly impartial manner, and if one part does not 

 absorb its proper quantity, it cannot be because it 

 is of less use than other parts which absorb more 

 than their share. It is the same with animals ; in a 

 case of dearth of food all parts suffer together, and 

 when there is abundance all rejoice. Dr. Eoux's 

 hypothesis is a pathological one ; healthy parts out- 

 grow unhealthy ones. It may account for sports or 

 for monstrosities, but it gives no explanation of 

 ordinary variations. 



Professor Hering's hypothesis is very simple and 

 supplies an explanation, both of heredity and of 

 variation. It is, in brief, that growth and eel! 

 division are constantly taking place through assimi- 

 lation, and that the direction of growth is guided by 

 unconscious memory. 



It may be objected that Bering is not warranted 

 is assuming that, because the brain receives impres- 

 sions from the peripheral nerve-endings, therefore 

 the germ-cells may do the same. But I think he 

 is right. We infer that impressions are made on 

 the brain, because the sensations, or ideas, can be 

 recalled at will ; and we see in memory a proof 

 that the brain has been affected. But we also see 

 the germ-cell, as it develops, recalling all the opera- 

 tions that its parents went through. If this is not 



