64 Life and Death, Heredity and Evolution 



Thus in general, until very recently at least, the experience 

 of investigators has been such as to confirm what was said 

 many years ago by that greatest of investigators of the 

 Protozoa, Emile Maupas. In 1888 Maupas, after long con- 

 tinued study of Protozoa, said: 



"In long and numerous experiments on fifteen to twenty 

 species, I have never observed anything which permits belief 

 in the existence of morphological and physiological differ- 

 ences between, not merely the products of a given fission, 

 but even among all those which have descended from such a 

 fission by regular and continuous generations." 2 



The same sort of results have been reached from the 

 study of higher organisms when they reproduce without mix- 

 ture, the progeny arising from a single parent instead of 

 two. The most famous work of this sort is the study of 

 self-fertilizing beans, made by Johannsen (1903). Diverse 

 races existed, but in seven years of selection no effect was 

 produced on the characters studied, so long as the selection 

 occurred within the limits of a single race. Lashley (1915) 

 studied Hydra in the same way ; no effect was produced from 

 selection continued for many generations. Ewing (1916) 

 attempted to modify by selection plant lice multiplying 

 par then ogenetic ally. The work extended over eighty-seven 

 generations, and many different characters were investigated 

 for longer or shorter periods. In no case could he change 

 the hereditary characteristics by selection. Agar (1914) 

 studied in a similar manner certain of the lower Crustacea 

 multiplying by parthenogenesis, and reached the same re- 

 sults. A great number of investigations could be cited, all 

 ending in the same way. The organisms studied contained 

 many diverse races. But when a single race or "line" is 

 studied, not mixing with other races, the differences between 

 'Maupas, 1888, p. 176, 



