TRANSLATORS INTRODUCTION 



INQUIRY into the problems of heredity is beset with 

 many difficulties, of which not the least is the 

 temptation to argue about the possible, or the 

 probable, rather than to keep in the lines of obser- 

 vation. Setting out from a laborious and beautiful 

 series of investigations into the anatomy of the 

 Hydromedusse, Weismann came to think that the 

 organic material from which the sexual cells of 

 these animals arose was not the common protoplasm 

 of their tissues, but a peculiar plasm, distinct in its 

 nature and possibilities. In the course of several 

 years, Weismann not only continued his own in- 

 vestigations in the many directions that his con- 

 ception suggested, but made abundant use of that 

 new knowledge of the nature and properties of cells 

 which has been the feature of the microscopy of 

 the last decade. His theory of the germplasm 

 gradually grew, undergoing many alterations, so 

 that even in its present form he regards it as tenta- 

 tive. Neglecting the numerous modifications and 

 accessory hypotheses by which he has sought to 

 adapt the theory to the phantasmagorial complexity 

 of organic nature, the main outline of the theory is 



