722 INHERITANCE 



point in the author's Genetics of the Protozoa (1929, pp. 261-70). 



Moewus (1934b) has made extensive studies of inherited environ- 

 mental modifications in structural characters in Chlamydomonas de- 

 baryana. This species is known to occur in many varieties differing 

 slightly in form, size, and structure; Moewus describes and figures twelve 

 of these. The different varieties are found in nature; also they occur 

 under different cultural conditions in the laboratory. 



Moewus found that he could transform the different varieties one into 

 another by the use of different culture media. But the transformation did 



Table 14: Environmental Modifications, Chlamydomonas deharyana; 

 Relation of the Number of Days Cultivated in Peptone Medium 

 TO THE Number of Days in Salt-Sugar Medium Required to Trans- 

 form THE Organisms from Type 1 to Type 5 (From Moewus, 1934b) 



Da-js in Peptone 

 as Type i 



Days in Salt'Sugar Medium 



Required for Transformation 



to Type 5 



28 

 140 



441 

 567 

 609 

 644 

 672 

 690 



28 

 49 

 133 

 17? 

 i3i 

 370 

 459 

 531 

 534 



not occur at once, on transfer to the different culture medium; on the 

 contrary, many generations in the new culture medium were necessary to 

 induce the transformation. 



An extremely important relation was observed to hold as to the time 

 required for the transformation. The longer a stock has remained under 

 conditions producing a given type, the greater the time and the number 

 of generations required to transform it to a new type, when placed under 

 new conditions. An example will illustrate the operation of this principle. 



Individuals in peptone culture are of type 1. If transferred to a ""salt- 

 sugar" infusion, they transform to type 5. If they have been only a few 

 generations in the peptone culture, the transformation in the salt-sugar 

 medium occurs very quickly. But if they have lived for a long time in the 

 peptone medium, a long time is required for transformation to type 5. 



