12 MENDELISM CHAP. 



Heredity, as it was termed, expresses with fair accu- 

 racy some of the statistical phenomena relating to 

 the transmission of characters in a mixed population. 

 But the problem of the way in which characters are 

 distributed from gamete to zygote and from zygote 

 to gamete remained as before. Heredity is essen- 

 tially a physiological problem, and though statistics 

 may be suggestive in the initiation of experiment, 

 it is upon the basis of experimental fact that progress 

 must ultimately rest. For this reason, in spite of its 

 ingenuity and originality, Galton's theory and the 

 subsequent statistical work that has been founded 

 upon it failed to give us any deeper insight into the 

 nature of the hereditary process. 



While Galton was working in England the 

 German zoologist, August Weismann, was elabora- 

 ting the complicated theory of heredity which 

 eventually appeared in his work on The Germplasm 

 (1885), a book which will be remembered for one 

 notable contribution to the subject. Until the pub- 

 lication of Weismann's work it had been generally 

 accepted that the modifications brought about in the 

 individual during its lifetime, through the varying 

 conditions of nutrition and environment, could be 

 transmitted to the offspring. In this biologists were 

 but following Darwin, who held that the changes in 

 the parent resulting from increased use or disuse of 

 any part or organ were passed on to the children. 

 Weismann's theory involved the conception of a sharp 

 cleavage between the general body tissues or somato- 

 plasm and the reproductive glands or germplasm. 

 The individual was merely a carrier for the essential 

 germplasm whose properties had been determined 



