490 Organisms Are Products of 



them fashionably small. In each genera- 

 tion the body or soma was changed by 

 this practice; a new character was ac- 

 quired. But measurements showed that 

 in those many generations the size of the 

 foot had not decreased - the acquired 

 character had not been inherited. 



A most interesting experiment was per- 

 formed by two American scientists. They 

 removed the ovaries from a pure black 

 (BB) guinea pig. Naturally every egg 

 produced by this guinea pig had a gene 

 for blackness. They transplanted these 

 ovaries to the body of a white {ww) 

 guinea pig in place of its own ovaries. 

 After a while this white female was 

 mated with a white male {^v^l'). You 

 would expect two white guinea pigs to 

 produce white offspring. But what were 

 the results? All the offspring were black! 

 It is clear that the genes for blackness in 

 the transplanted ovaries were not affected 

 by the body of the wio female. Other 

 biologists have performed experiments 

 of many kinds on many types of animals 

 and plants to find out whether acquired 

 characters can be inherited. In all these 

 experiments the results show that ac- 

 quired characters are not inherited. 



(Optional) The environment affects the 

 action of genes. It is clear from what you 

 have just read, that the environment af- 

 fects the body or soma, causing changes. 

 We have all noted this. We know, too, 

 that these changes are not inherited. 



It is also true, however, that the en- 

 vironment is important in making it pos- 

 sible for a gene to produce its effect. For 

 example, all green plants have genes for 

 the production of chlorophyll. Yet in 

 most plants these genes do not produce 

 chlorophyll unless the plant is in the light. 



Heredity a?id Enviromnent iixi r i\ 



Fig. 439 This corn contains genes for the pro- 

 dtictioii of red kernels. But red kernels are 

 produced only when light reaches them. Pro- 

 fessor R. A. Emerson cut away part of the husks 

 in the second and fourth ears. How did the 

 word SUN appear? (Brooklyn botanic garden) 



The light affects the action of the genes. 

 How light affects the action of the genes 

 in a certain variety of corn is strikingly 

 shown in Figure 439. 



Sometimes temperature, too, has a pro- 

 found effect on a particular gene. In 

 some fruit flies there is a gene for ves- 

 tigial (shortened) wing. But the size of 

 the vestigial wing is determined not only 

 by a gene but by the temperature of the 

 fly's surroundings. If the fly is raised at a 

 high temperature in an incubator the 

 vestigial wing is nearly as long as the 

 wing of a normal fly. 



x-Xmong Chinese primroses there is one 

 variety that has genes for white flowers; 

 another variety has genes for red flowers. 

 But there is a third variety that has genes 

 that produce different colors depending 

 on the temperature in which the plant is 



