ALCOHOLIC FERMENTS. 181 



attenuation at the end of the primary fermentation. The same, 

 was found to be the case with other species. 



(B) HANSEN also succeeded, by cultivation in nutrient gelatine 

 in producing new constant varieties or species. 



Thus, two varieties of Carlsberg low-fermentation yeast No. 1 , 

 each generation of which was transferred to the surface of 

 wort-gelatine, attained a fermentative power superior to that of 

 the original forms. 



It was observed in the experiments on spore-transformations 

 brought about by the action of temperature and aeration, that 

 if cells of the successive generations are selected, many had 

 been affected even in the first growths under the new con- 

 ditions ; this modification, however, is only temporary in its 

 character; it is only after successive generations have been 

 allowed to develop through continued inoculation under the 

 new conditions that the acquired characters become constant. 

 It appears from this that the transformation does not depend 

 on temperature or aeration alone, but also on the nutrition and 

 propagation of the cells. 



A comparison of these different factors has, however, shown 

 that they contribute unequally to the result. Both the nutrient 

 liquid and the aeration only bring about vigorous new-forma- 

 tions, and may therefore vary considerably without materially 

 affecting the result. This, however, is not true of temperature ; 

 a fluctuation of a few degrees is sufficient to prevent the 

 variations described from coming into existence. Hence, it 

 follows, that temperature plays the principal part in these 

 trans formations. 



No objection can be raised to the view that we are possibly 

 dealing with the formation of new species. We know in fact 

 that the species are not fixed and unchangeable, as was 

 generally assumed in LINNE'S time, but that the characters 

 of a species are only constant under certain conditions. The 

 complete elucidation of these important and intricate problems 

 can, however, only be effected by a series of experiments 

 carried on through a long period of time and under a variety 

 of conditions. 



As previously stated, these remarkable changes are only 

 brought about by a long-continued and violent interference 



