Varietäten, Descendenz, Hybriden. 211 



Barber, M. A., On Heredity in certain Micro-Organisms. 

 (Kansas University Science Bull. IV. W. 1. 1907.) 



In the introduction the author discusses the physiological and 

 morphological changes which certain yeasts undergo from genera- 

 tion to generation, giving a comparative summary of work previous 

 to his own. He goes on to discuss certain experiments which he 

 conducted to determine whether distinctive morphological and phy- 

 siological characters could be transmitted by heredity in yeasts and 

 in certain bacteria. For the j^easts he worked with Sacchayoinyces 

 anomahts which he got on various media. He found a distinctive 

 type of cell characterized by long lilamentous processes. 



The results of the work with the yeast are summed up as 

 foUows : 



1. Continued selection of cells of more than average size does 

 not permanently modify the type. 



2. Variations occur in this species, which, like mutations in 

 higher plants, are capable of giving rise to races endowed from the 

 beginning with characteristics differing from those of the type. 

 These variations are apparently independent of the immediate con- 

 ditions of cultivation. 



3. New races arising from these variations are characterized 

 morphologically by cells abnormally elongated and tending to adhere 

 in groups, and by a partial loss of the power of producing spores. 



4. These morphological characteristics have persisted in cultures 

 continued through three years and five months in a great variety 

 of media, and a new race successfully competes with the parent 

 stock when mixed with it in cultures. 



5. Selection in the direction of further modifying the new races, 

 or of bringing them back to the type have alike failed to perma- 

 nently alter the new characteristics. 



6. There is evidence that the new races have a greater power 

 of resisting hat and drying, a slightly greater power of fermenting 

 the sugars and a somewhat less power of liquefying wort gelatin 

 than the type. 



His work with bacteria consisted in experiments with Bacillus 

 coli connminis , for which his findings are as follows: 



1. Variations arise in Bacillus coli cofninunis, which, like those 

 of Saccharoniyces anomalus , may give rise to races exhibiting per- 

 manent morphological characteristics not possessed by the type. 



2. These variations arise suddenly, and apparently independently 

 of conditions of cultivations; and are to be compared with mutants 

 observed in higher plants. 



3. They show, in general, a tendency to diminished rapidit}' of 

 growth at the beginning, but, having once begun to develop, they 

 produce, as a rule, cultures as vigorous as the normal. 



4. They are of different types, and the new races arising from 

 them may be characterized by an abnormal tendency to produce 

 long filaments, or by a nearly complete loss of motility. 



5. These new races vary in the degree of their deviation from 

 the type and in their stability. While some apparently require more 

 than one selection to preserve their fixity, others have been constant 

 from the first selection over a period of "two years and eight months. 



6. One new race further differs from the type in exhibiting an 

 increasing power of fermenting sugars, and a partial loss of sensi- 

 tiveness to agglutinating serums. 



At the end of the paper a description is given of a new method 



