SIGNIFICANCE OF SEXUAL REPRODUCTION, 



ETC. 



-♦-♦- 



PREFACE. 



The greater part of the present essay was delivered at the 

 first general meeting of the Association of German Naturalists, 

 at Strassburg, on September i8th, 1885, and is printed in the 

 Proceedings of the fifty-eighth meeting of that Society. 



The form of a lecture has been retained in the present pub- 

 lication, but its contents have been extended in many ways. 

 Besides many small and a few large additions to the text, I 

 have added six appendices in order to treat of certain subjects 

 more fully than was possible in the lecture itself, in which I was 

 often obliged to be content with mere hints and suggestions. 

 This appears to be all the more necessary because it is im- 

 possible to suppose that many views and ideas upon which the 

 lecture was based would be well known to all readers, although 

 they have been described in my former papers. It was above 

 all necessary to deal with the class of acquired characters, 

 which, as it seems to me, is easily confounded, especially by 

 the medical profession, with the much broader class of new 

 characters generally. Only those new characters can be called 

 ' acquired ' which owe their origin to external influences, and 

 the term 'acquired' must be denied to those which depend 

 upon the mysterious relationship between the different heredi- 

 tary tendencies which meet in the fertilized ovum. These 

 latter are not ' acquired ' but inherited, although the ancestors 

 did not possess them as such, but only as it were the elements 



