108 PROCEEDINGS OF THE AMERICAN ACADEMY 



Leptothrix threads, which seem to precede spore formation, begin to 

 form, and within thirty-six to forty-eight hours the spores api'ear. It 

 will be remembered that Kern gives two distinct methods of spore 

 formation, — one occurring in isolated cells, and the other in the 

 Leptothrix threads. It is no wonder, therefore, that neither method 

 has received general credence. My investigations on the North 

 American form have led to results diametrically opposed to those of 

 Kern. First, I found but one method of spore formation ; secondly, I 

 found this method occurring only in the Leptothrix threads, although 

 I sometimes found isolated cells bent or curled in such a manner 

 that spore formation was well simulated. Spore formation in the 

 Leptothrix threads takes place as follows. At each end of every cell 

 of the thread a small bright dot appears, which becomes brighter, 

 larger, and much more highly refractive than the rest of the cell, until 

 finally it assumes a well defined spore wall and develops into a mature 

 spore. Each cell has therefore two spores, one at each end, and each 

 originating independently of the other. In no case did I see two 

 spoi'es formed, as Kern states, by the division of a single agglomerated 

 mass of protoplasm into two portions. 



There are two or three other important points in which the Ameri- 

 can alcoholic milk-ferment closely resembles the Caucasian kephir. 

 So far as I know, no one has ever tried the experiment of making 

 the North American yeast cause the alcoholic fermentation of milk. 

 Struck with its gross and microscopic resemblances to kephir, I was 

 induced to try the experiment, and to my pleasure I obtained 

 alcoholic fermentation, the evolution of carbonic acid gas being 

 suflftcient to force the cork from the flask. I easily obtained a large 

 precipitate of CaCOs from lime-water by the usual test for carbonic 

 acid gas. The presence of alcohol was proved by the iodiform test. 

 Since ethyl alcohol, Co H5OH, cannot be detected in the presence of 

 lactic acid, CsHgOg, (for lactic acid forms iodiform as easily as ethyl 

 alcohol,) I neutralized with Na^COs after filtering off the fluid por- 

 tion of the milk, distilling finally the neutralized filtrate. Thus every 

 trace of lactic acid was removed. With KOH and iodine the dis- 

 tillate gave iodiform, thus proving the presence of alcohol. This fact 

 alone, viz. that this yeast causes alcoholic fermentation of milk, is 

 sufficient to establish a near relation to the Caucasian kephir. More- 

 over the fermented milk agrees closely with the description of the 

 kephir drink. The milk does not sour in the ordinary sense, for it 

 does not coagulate in large masses ; still it is acid, contains some 

 carbonic acid gas and alcohol, and is by no means unpleasant to the 

 taste. 



