viii Translator s Preface* 



the results arrived at by the minute and laborious 

 investigations with which Dr. Weismann has for 

 many years occupied himself. I may however 

 point out that before the appearance of the 

 present work the author, in addition to his well- 

 known papers on the embryology and develop- 

 ment of insects, had published two valuable con- 

 tributions to the theory of descent, viz. one 

 entitled "Uber die Berechtigung der Darwin'schen 

 Theorie" (1868), and another " Uber den Einfluss 

 der Isolirung auf die Artbildung " (1872). These 

 works, which are perhaps not so well known in 

 this country as could be desired, might be advan- 

 tageously studied in connection with the present 

 volume wherein they are frequently referred to. 



Since every new contribution to science is a 

 fresh starting-point for future work, I may venture 

 without any great breach of propriety to dwell 

 briefly upon one or two of the main points which 

 appear to me to be suggested by Prof. Weis- 

 mann's investigations. 



Although the causes of Glacial Epochs is a 

 subject which has much occupied the attention of 

 geologists and physiographers, the question is one 

 of such great complexity that it cannot yet be 

 regarded as finally settled. But apart from the 

 question of causes a most able discussion of 

 which is -given by the author of " Island Life " 

 there is not the least doubt that at no very 

 distant geological period there occurred such an 



