The choline‐containing teichoic acids of pneumococci can be modified by biosynthetic replacement of the choline residues with certain structural analogues, such as ethanolamine (EA) or the N‐monomethyl‐ (MEA) and N‐dimethyl‐ (DEA) amino derivatives of ethanolamine. Cells containing such analogues in their teichoic acids develop pleiomorphic alterations in several physiological properties, which include resistance to detergent‐induced lysis and inhibition of cell separation (chain formation). We report here the results of physiological studies on the mechanism of these two phenomena. Our results are summarized in the following: (a) Pneumococci grown on various amino alcohols produce cell walls of identical amino sugar and amino acid composition. (b) Both choline‐ and EA‐containing teichoic acids seem to follow the same conservative pattern of segregation during growth and cell division. (c) Lysis sensitivity of pneumococci requires the juxtaposition of lysissensitive (choline‐containing) cell walls and endogenous autolysin at the cell wall growth zone. (d) Upon readdition of choline to ethanolamine‐containing cells, lysis sensitivity and catalytically active (C‐type) autolysin reappear in the bacteria with the same kinetics. (e) The chains of EA‐grown pneumococci contain fully compartmentalized cells and normal cross walls.