STUniES ON FERMENTATION. 139 



borders.* In this state, cells are generally dead and incapable 

 of any revival. It is impossible to avoid being impressed by 

 the striking analogies which exist between all these facts and 

 those presented by cells of yeast. 



In concluding our study of the vegetation of mucor as a 

 mould and mucor as a ferment, we may again remark that 

 the most striking analogies also exist between the preceding 

 observations and those we have seen in the case of penicillkun 

 as})ergillus, and mycoderma vini. These latter plants do not 

 furnish alcohol or carbonic acid gas by direct fermentation 

 of the sugar, as long as we let them vegetate with plenty 

 of air at their disposal. Once submerged, however, their vital 

 aspect changes ; on the one hand the cells or filaments of 

 the mycelia evince a tendency to become larger ; on the other 

 hand there is a tendency to greater closeness in these latter, 

 and, consequently, a transition to the state of conidia. Lastly, 

 there is a correlative budding of cells, accompanied by a 



* The figure given below supplies this omission. The cells that are 

 isolated or are in chains, b.b.b., show this state of the old cells. The 

 cells a.a.a. are younger, and may be more easily revived. We may see 

 by the dimensions of some of these how greatly, in certain cases, the 

 cells of mucor resemble cells of yeast ; nevertheless, in the state of the 

 contents and the aspect of the outlines, there are always some differences 

 sufficiently appreciable to strike the practised observer. 



4(3 



Fig. 23. 



The figures adjoining the cells indicate fractions of a millimetre. (A 

 millimetre may be taken as gV'iiiO 



