Earlier Theories of Heredity 7 



acters intelligible by an appeal to any known force has 

 often been felt, but no one has hitherto cast doubt upon 

 the very existence of such a form of heredity." The 

 general belief of the time that the inheritance of acquired 

 characters was a fact came from two sources: (i) many 

 examples of the inheritance of acquired characters 

 were being reported; and (2) inheritance of acquired 

 characters was thought necessary to explain evolution. 

 Weismann therefore faced two problems: (i) to explain 

 away the reported cases of the inheritance of acquired 

 characters; and (2) to provide a theory which would 

 make evolution possible without the inheritance of 

 acquired characters. 



He took up individually the many reported cases 

 of such inheritance and discredited them one after 

 another, showing convincingly how they could be 

 explained in some other way. He also cited from his 

 own experience numerous cases in which the inheritance 

 of acquired characters was distinctly absent. As a 

 result of his investigation of these cases, he developed 

 his theory of germinal continuity, commonly spoken of 

 as continuity of the germ plasm, a theory which is in good 

 standing today. In the attempt to provide a theory 

 which would make evolution possible without the 

 inheritance of acquired characters Weismann dis- 

 tinctly failed. To explain variation, which is the 

 basis of evolution, he proposed the theory of germinal 

 selection, which is even more imaginative than Dar- 

 win's transportation hypothesis. As a consequence 

 Weismann's experience was much like that of Darwin. 

 His theory of germinal continuity has fairly well stood 

 the test of later investigation and is still current among 



