BOTANICAL SUBJECTS. 43 



" On the other hand, all the changes which have taken place 

 in the evolution of flat fishes are such as must have taken place in 

 accordance with known physiological effects in individual fishes 

 which, after a certain period of development, adopted the habit of 

 lying on their sides on the sea -bottom." . . . 



He concludes by stating that " all that is necessary to prove 

 that acquired characters are inherited , in the sense in which the 

 words ought to be used, is to show that an external influence 

 of the same kind and the same degree produces more effect in 

 every generation than in the preceding." And, it might be 

 added, may produce characters which will become so fixed as to be 

 congenitally inherited, even when the surroundings are eventually 

 altered. 



If the cells of the foetal individual are sensitive at all, there 

 must be a continual play between it and its surroundings. If the 

 foetal envelopes, whatever those may be, are transparent, light will 

 play upon them ; if they are conductors of heat, this will play 

 upon them. The most subtle of all agents, however, are electrical 

 and magnetic influences. They penetrate everywhere, and are 

 omnipresent. 



In animals which have a differentiated nervous system, the 

 play on the atoms may largely take place through the nerve-cells 

 and nerves, these being played upon by surroundings. 



It is inconceivable that the changes during foetal life, which 

 must be so dependent on atomic electrical changes, should not 

 be influenced by the electrical changes of the parent, and these 

 in turn influenced by the electrical changes of the parent's 

 surroundings. 



Considering that the atomic compositions and decompositions of 

 organisms are governed by electrical attractions and repulsions, 

 the wonder is, not that surroundings should influence the changes 

 which occur in foetal life, but that seemingly they have so little 

 influence, owing probably to the more potent influence of heredity. 

 It is only the persistence of surrounding influences acting im- 

 perceptihly and by very slow degrees, which eventually overcomes 

 the pre-established inherited influence. So that we can see any 

 marked deviation only after long periods. Geological periods, 

 although very long, compared with human life, if measured by the 

 clock of the universe, become comparatively short periods. 



