No. 529] 



ORGANIC RESPONSE 



15 



and are not transmissible, which is in accord with the 

 main body of evidence upon this point. There are, how- 

 ever, a number of records of the appearance of definite 

 qualities or morphological characters in the yeasts, 

 which were transmissible and permanent. These de- 

 partures were so striking as to be capable of being re- 

 garded as mutational, and their origin has been ascribed 

 to the influence of the environment by experimenters of 

 notable skill, such as Beijerinck, Winogradsky, Lepesch- 

 kin, Hansen and Barber. It may be recalled in this con- 

 nection, that environic responses are generally sudden, 

 ami that the entire range of departure may be made in 

 a single generation, at most in two or three. 7 



Pringsheim after a comprehensive review of his own 

 work and of other available evidence obtained by a study 

 of accommodations or adaptations of yeasts and bacteria 

 to unusual temperatures, culture media, and poisons, 

 concludes that some of these variations are fixed 

 and transmissible both asexually and by spores, while 

 others are not. It is not easy to analyze contributions 

 upon this subject with reference to the differential action 

 of the exciting agencies upon soma or germ-plasm, 

 neither is it clear as to the action of the selection in the 

 experimentation. It is important, however, to note that 

 the alterations concerned are direct functional responses 

 to the exciting agencies. 8 



The researches of Jennings with paramcecium deals 

 with conditions of morphology and physiology not widely 

 dissimilar from those offered by the bacteria with regard 

 to the present problems, and his work has been carried 

 out with an extensiveness and thoroughness impossible 

 to the worker with more massive and more slowly moving 

 organisms. Cultures were carried through hundreds of 

 generations with no progressive action in fluctuating 



