OF ARTS AND SCIENCES. 



107 



general appearance, for it cannot invert cane-sugar as ordinary beer 

 yeast sliould do. Although I cultivated it in saccharose solutions of 

 all strengths, it never caused a trace of fermentation. As soon, 

 however, as T placed the yeast in a grape-sugar solution, i. e. a solu- 

 tion of dextrose, fermentation ensued. Unfortunately, Kern did not 

 try the effect of his yeast upon saccharose, and we are therefore 

 unable to compare his yeast with that found in American kei)hir iu 

 this important point. But the absence of information can hardly be 

 urged as an evidence that the two forms are not the same. Again, 

 ordinary beer yeast forms spores, while the kephir yeast does not, 

 thus affording another reason for reganliog them as distinct species. 



Beyerinck has described the yeast which occurs iu the Caucasian 

 kephir grain in the " Ceutralblatt fiir Bakteriologie," Vol. VI. page 

 44, naming it Saccharotuyces kefyr with the following distinguishing 

 characteristics : — 



(i.) The cells are of various sizes and shapes, from spherical to 

 elliptical, the former measuring from 3.2 /a to 6.4 /x in diameter, and 

 the latter varying from 3.2 /x- 9.6 /a in the major axis to 3.2 /a — 6.4 /i 

 in the minor. 



(2.) The yeast is associated with a rod-shaped Bacterium in a 

 granular mass. 



(3.) The yeast is not able to ferment saccharose or cane-sugar. 



(4.) It is able to ferment lactose or milk-sugar. 



(5.) It has no known spore formation. Since the North American 

 yeast agrees with all these characteristics, while it differs in an im- 

 portant point from S. cerevisice, it will be sufficient for the present 

 purpose if I apply the name S. kefyr to our American fosra without 

 attempting to discuss at lengtli disputed points in synonymy. 



Let us turn now to the Bacteria. The cells are short cylindrical 

 rods with homogeneous protoplasm, varying fiom 8.5 fx. to 4.5 yu, long 

 by 0.8 /x broad ; precisely agreeing with Kern's measurements. The 

 cells increase by splitting perpendicularly to the long axis, the result- 

 ing cells being somftimes joined together, thus producing Leptothrix- 

 like threads of all lengths, even to I20yu., and sometimes completely 

 separated. Many oi the isolated cells possess the power of motion, 

 but after repeated efforts I was unable to demonstrate the presence 

 of cilia. 



It is not such an easy matter to induce these cells to form spores as 

 Kern implies that it was in the case of his B;cteria. The best method 

 is to place a clump of the yeast in a watch-crystal with a little water, 

 covering the whole with another crystal. In twenty-four hours 



