INTRODUCTION 15 



and elaborated fashion than has been possible 

 hitherto. This course is the more imperative, as 

 in his recent magnum opus on the germplasm 

 Weismann has propounded a theory of evolution 

 wrought with the greatest care and acuteness, and 

 totally irreconcilable with my conclusions. The 

 chief differences between my views and those of 

 Weismann have now become clearer and more 

 tangible than ever. It is true that in my text- 

 book, On the Structure and Function of Cells, 1 

 published in the autumn of 1892, I gave a short 

 account of my theory of heredity in chapter ix., 

 ' The Cell as the Material Beginning of the 

 Oro-anisni.' But in that I could not deal with 



o 



Weismann's work, which appeared simultaneously, 

 and, moreover, in a text-book it was impossible to 

 do more than sketch my views. 



My present task is twofold ; it has both a positive 

 and a negative side. First, I have to examine the 

 arguments recently alleged in favour of the theory 

 of preforrnation, testing them to reveal their in- 

 herent weaknesses, and to controvert their fallacies. 

 As Weismann unquestionably is the chief of those 

 who have advocated preformation, and has made a 

 closed system of it again, it is necessary for me to 

 take special notice of his conception as it is set 

 forth in The Germplasm. Although I am no friend 

 of polemic, the case demands it. For the decision 

 of a question so momentous as the relative scopes 

 of evolution and epigenesis in embryology must 



1 An English translation, The Cell, was published by Swan 

 Souneuschein and Co. in 1895. 



