88 Life and Death, Heredity and Evolution 



the like, and determined whether their descendants inherited 

 their peculiarities. 



Barber discovered the same thing that others have found 

 in other organisms ; in the very great majority of cases such 

 peculiarities within a race are not inherited. Great num- 

 bers of indivduals selected for certain peculiarities gave 

 offspring of the usual types. Nevertheless a few heritable 

 variations were discovered. In Bacillus coli, 140 individuals 

 that were longer than usual were isolated. All but one 

 gave descendants of the usual size, but this one gave a race 

 having bodies longer than usual. The race was permanent ; 

 selection of longer and shorter specimens within it was 

 without further effect. Two other long-bodied races were 

 obtained in later extensive selections. Similarly, from among 

 a great number of selections of peculiarly shaped yeast cells, 

 a number of new races were obtained in which the cells 

 were narrow and elongated, as compared with the more 

 nearly spherical cells of the parents. 



What caused the production of these new races is not 

 known, but they demonstrate that in bacteria and yeasts at 

 times the inherited characteristics of a race become altered. 



More definite results have been reached in the study of 

 color changes in bacteria. The organism known as Bacillus 

 prodigiosus produces a bright red color; it is supposed to 

 be the cause of the "miracles" in which the bread of the host 

 appears to become bloody. Wolf (1909) attempted by 

 various means to obtain from this organism races that give 

 a different color or that are colorless. A series of fifty 

 successive selections of the lightest parts of the colonies 

 produced no inherited effects; the descendants were still of 

 the typical color. 



Wolf further tried cultivating the colored bacilli on media 

 containing chemicals of various sorts. He employed in dif- 

 ferent cases copper sulphate, potassium bichromate, carbolio 



