14 THE AMERICAN NATURALIST [Vol. XL V 



by investigations, nsing a more perfected technique, and 

 having the advantage of a keener insight into the real 

 nature of the problems to be solved. 



That the general hypothesis with its corollaries is 

 being subjected to the most critical examination and that 

 the assumptions implied in the conception of inheritance 

 of acquired characters are being put to exact and conclu- 

 sive tests, is readily apparent when a review is made of 

 recent and current researches in which living material 

 from widely separated groups of animals and plants is 

 being subjected to a variety of nutritive conditions and 

 climatic agencies. Klebs, who has long been concerned 

 with the morphogenic reactions of plants, has determined 

 a series of conditions under which the stages of mycelial 

 development, asexual zoospore and sexual or oospore 

 formations in filamentous fungi may be inhibited or var- 

 iously interchanged. Much more important reactions 

 were obtained from Sempervivum, the live-forever of the 

 garden. In this plant, inflorescences were replaced by sin- 

 gle flowers by experimental excitation while it was found 

 the number and arrangement of the floral organs as well 

 as of the stamens and carpels could be altered. Further- 

 more, the deviations in question were found to be trans- 

 missible to the second or third generation in guarded seed- 

 roj reductions. 6 



Microorganisms with a short cycle offer peculiarly ad- 

 vantageous material by reason of their simple reproduc- 

 tive processes, and also by the fact that it is possible to 

 control environic factors with exactitude. The volu- 

 minous literature of bacteriology shows that much at- 

 tention has been devoted to the building up of characters 

 by selection, and to the study of the behavior of morpho- 

 logical divergences occurring in special cultures. 



The experiments of Buchanan with Streptoccus lacti- 

 cus yields the conclusion that phases of fluctuating varia- 

 tions in the bacteria induced by cultures may not be fixed, 



