540 EVOLUTION, HEREDITY, EUGENICS 



no certainty about maternal inheritance of tuberculosis, but it is 

 possible that there is inherent predisposition. Antitoxins and im- 

 mune bodies may apparently be transmitted through the egg. 



Monstrosities in fishes and echinoderms by alteration of the salt 

 constituency of the water are not heritable. Roberts increased the 

 size of vestigial wings in a race of Drosophila by high temperature. 

 Under normal temperature the effect did not persist. Castle and 

 Phillips transplanted guinea-pig ovaries, black to white, demonstrat- 

 ing that the soma has no influence in determining color of the off- 

 spring. Griffith found that direction of rotation of rats is specific 

 in the type of disequilibration produced. Kammerer supplied light 

 stimulus to cave animals and procured eye development. Pictet 

 fed gypsy moths walnut instead of oak leaves, and induced a lighter 

 color, which persisted for only two generations. Johannsen proved 

 that the effect of parental starvation wears off in just a few genera- 

 tions. 



II. Can Environment Induce Mutations? — Arsenic, quinine, mor- 

 phine, alcohol, ether, and other poisons affect the first generation 

 only in Drosophila. 



Plough (1917), by two consecutive days' exposure of the females 

 to high temperature (31.5° C), was able to increase the percentage 

 of crossing over in chromosomes II and III of Drosophila. His 

 study showed that crossing over in Drosophila does not take place 

 in the early oogonial divisions. He considers that his work does 

 not bear on mutations but explains the mechanism of crossing over. 

 Mavor (1921) x-rayed female Drosophila and produced non- 

 disjunction (page 539) of the X-chromosomes, as shown by an 

 increased number of exceptional males and exceptional females in 

 the first generation. These females continued to produce ex- 

 ceptional offspring! Later (1924) as a special case of non-disjunc- 

 tion, he produced gynandromorphs. Mavor and Svenson (1924) 

 increased the percentage of crossing over in chromosomes II and III 

 of Drosophila by x-raying the virgin females one day prior to mating. 

 Little and Bagg (1924) used x-rays on mice, with results suggest- 

 ing induction of a new gene. MuUer (1927) exposed sperms of 

 Drosophila to rather heavy doses of x-rays and produced " gene 

 mutations " in a large number of the germ cells. He succeeded in 

 producing with the treated sperms a number of familiar mutants 

 such as " white eye " and " forked bristles " as well as other en- 



