ZOOLOGY AND EOT AN Y^ MICROSCOPY^ ETC. 105 



tlie assistance of man. Similar experiments with PenicilUum altogether 

 failed ; but this was probably the result of conditions of temperature, 

 a temperature of 34°-38° C. destroying the germinating power of the 

 spores of PenicilUum. Aspergillus nigrescens, on the other hand, while 

 thriving at the temperature of the body, did not develope in the 

 cornea ; the cause in this case being possibly its alkaline reaction. 

 LeptotJirix huccalis, which occurs abundantly in the mouth, was found 

 to develope also in the cornea, undergoing no change from its altered 

 conditions. The author's experiments on this point were altogether 

 favourable to the view of the constancy of species. 



Physiological Effects of various Ferments.* — Ph. Van Tieghem 

 reports the results of a series of investigations made by M. Gayon on 

 the influence of various ferments on different fermentable liquids. 



Mucor circinelloides, when vegetating without free oxygen, behaves 

 precisely like Saccharomyces cerevisice in contact with the wort of 

 wine or beer ; the beer obtained from it being very limpid and of a 

 sweet somewhat plum-like taste. But with cane-sugar this organism 

 produces no inversion, and consequently no fermentation. But if 

 into the liquid is introduced a small quantity of invertine, or any 

 fungus, like PenicilUum, which produces invertine, fermentation of 

 the inverted sugar immediately sets up ; and the Mucor, acting from 

 this time like PenicilUum, destroys first the glucose, and then the 

 levulose. 



In the absence of the power of inverting cane-sugar Mucor 

 circinelloides vesembles M. spinosus SkudMucedo and Bliizopus nigricans; 

 and these experiments determine directly for the first time that the 

 inversion of cane-sugar must necessarily precede its fermentation, in 

 other words, that it is not directly fermentable. The various sj)ecies 

 of Saccharomyces behave differently in relation to cane-sugar; some, like 

 S. cerevisice, inverting it, while others, like S. apiculatus, are wanting 

 in this power. 



From these facts M. Gayon draws some applications which may 

 be of great importance from an economical point of view; as, for 

 example, in the separation of cane-sugar from other saccharine fluids, 

 for example molasses. The reducing sugar may be destroyed by 

 fermentation with Mucor, while the cane-sugar remains unaltered, 

 and may be crystallized. He is also able to account for the reducing 

 sugar which gradually forms in crude cane-sugar, and sometimes in 

 that of beet. This sugar is inactive, and if this results from its 

 essential nature the mixture ought, when fermented by Mucor, always 

 to preserve its primitive rotation to the right. If, on the contrary, it 

 is neutral because it consists of a compensating mixture of glucose 

 and levulose, then, when fermented with Mucor, the power of rotating 

 to the right ought to diminish as the glucose disappears, then to 

 increase from the destruction of the levulose, and finally reassume its 

 original value. Experiment favours this latter conclusion, and proves 

 that the reducing sugar is an inverting sugar, in which the opposite 

 powers of rotation exactly neutralize one another. 



* Ann. Sci. Nat. (Bot.) xiv. (1882) pp. 46-9. 



