THE CYTOPLASM 



by sorting out will inevitably enjoy a selective advantage during 

 development. Alternatively we may say that the mutation is due, 

 as with kappa, to a reduced concentration in a plasmagene that is 



Tl 



Fig. 44. — The origin and persistence of a defective capacity for development in 

 Phascolus vulgaris after treatment with chloral hydrate. P, parent; PT, treated parent; 

 T 1-6, derived generations (after Hotfmami, 1927). 



normally present, its regular concentration being recovered, as 

 Somieborn has suggested, when sexual reproduction affords a respite 

 to growth. 



Severe external shocks may have an effect, similar to the dauer- 

 modification of plasmagenes, on self-propagating substances released 

 into the cytoplasm by nuclear genes. Goldschmidt has found in 

 Drosophila that it is possible in this way to imitate the effects of gene 

 change by treatment of the pupae, producing what he has described 



184 



