720 INHERITANCE 



temperatures. As in the case of resistance to arsenic, the acquired toler- 

 ance slowly decreased and finally disappeared when the organisms were 

 cultivated at moderate temperatures. 



To such long-lasting modifications, inherited for many generations 

 but finally disappearing, Jollos gave the name Dauermodifikationen. This 

 designation is much employed, even in languages other than German. 

 Jollos interprets these modifications as affecting only the cytoplasm, not 

 the chromosomes; a matter to which we shall turn later. Phenomena of a 

 similar character have been described by Jollos and others in multicellu- 

 lar organisms. Hammerling (1929) has published an extensive sum- 

 mary of what are believed to be Dauermodifikationen in many organisms. 



Certain additional features of acclimatization in free-living Protozoa 

 are brought out in the work of Neuschloss (1919, 1920). He investi- 

 gated the acclimatization of P. caudatum to certain chemicals, particularly 

 to quinine, methylene blue, trypan blue, fuchsin; also to arsenic and anti- 

 mony. He found that he could induce increased resistance in about a 

 month by gradually subjecting the animals to increasing concentrations 

 of the substances. 



Neuschloss investigated the nature of the changes in the organisms 

 in the following way. After acclimatizing the organisms to an injurious 

 substance, two equal samples of that substance were taken, in concen- 

 tration somewhat greater than that to which the animals were resistant. 

 To one of these was added a large number of the acclimatized paramecia, 

 to the other an equal number of the unacclimatized animals. The animals 

 were in each case left in the samples until death occurred. After death, 

 the amount of injurious substance that had been removed by the organ- 

 isms from the solution was quantitatively determined. 



In all cases it was found that the acclimatized animals removed from 

 solution a much greater proportion of the injurious substance than did 

 the unacclimatized. In the case of the four organic compounds, the per- 

 centage removed from the solutions by the acclimatized and the unacclima- 

 tized animals were as follows: 



