Contents. 



Page 



A. Introductory 1 



B. His tori cal and Descriptive 3 



C. Comparative and Experimental Stud y (Tables I 



-VIII) 20 



I. Color determination of bacterial pigment 20 



II. Variability in the Prodigiosus group 23 



1. Introductory "23 



2. Discontinuous variation or mutation 24 



3. Range of normal variation 27 



a) Growth and pigment on ordinary culture media . . 27 



b) Growth and pigment on special solid media ... 29 



c) Growth and pigment in non-proteid media .... 35 



d) The effect of light upon pigment production ... 40 



4. Summary 42 



D. Notes on Groups of Red Chromogenic Bacilli . . 43 



I. The Prodigiosus group 44 



II. The Lactis erythrogenes group 44 



III. The Rubricus group 44 



Table IX 46 



Table X 48 



Bibliography 45 



Reference List of Other Red Chromogenic Bacteria .... 54 



1 si non 



