TRANSLATOR'S PREFACE 



(Zeus faber), which swims in a vertical position, the vertical 

 depth of the body is as great in proportion to the length as 

 in the young turbot, and greater than in the young brill. 



It may be thought that these facts are as much in 

 opposition to the view that the asymmetry of flat fishes was 

 evolved in consequence of the efforts of the ancestral fish to 

 use its lower eye after it had assumed the habit of lying flat 

 on the bottom. But it must be remembered that those who 

 believe in the inheritance of acquired characters also believe 

 that the modification caused by the habits of the adult is 

 inherited at an earlier and earlier age, until it may appear 

 long before the habits of the adult are assumed. 



To some extent the controversy concerning the inheritance 

 of acquired characters is due to an ambiguity of language. 

 The Neo-Lamarckians do not assert that a change produced 

 in an individual by functional activity or external conditions 

 is inherited at once and completely by that individual's 

 offspring; in this sense acquired characters are not usually 

 inherited. But what they do maintain is, that when a 

 certain functional activity produces a certain change in one 

 generation it will produce it more easily in the next, and so 

 on ; so that if a certain constant exercise of functional activity 

 is continued for a great number of generations, ultimately 

 structural modifications will appear in the young even before 

 the function which has produced them has commenced to be 

 exercised ; and this process may go on indefinitely, so that 

 at last the structural character in question will be inherited 

 for many generations after the exercise of the particular 

 function has altogether ceased. 



Nothing can test better the claims of the two theories, 

 the Neo-Lamarckian and the Neo-Danvinian, to be accepted 



