1. 1. A mutant strain of Streptococcus faecalis ATCC 9790 has been isolated that grows as long chains in medium of high salt content but as single cells or very short chains in low salt medium. 2. 2. Cell walls prepared from the chained form of this mutant autolyze more slowly than those from the unchained form. Both active and latent forms of the cell wall autolytic activity are less active in the chained cultures. 3. 3. Autolytic activities of cell walls prepared from chained and unchained cultures do not differ in their sensitivity to high salt concentrations. 4. 4. Chained, unchained and wild-type wall preparations treated to inactivate their endogenous autolytic activity serve equally well as substrates for soluble autolysin released from active chained or unchained cell walls. 5. 5. Autolysin from chained wall preparations dechains heat-killed cultures less rapidly than autolysin from unchained preparations. 6. 6. Taken together, the above observations suggest that chaining results from a lowered cell content of autolysin rather than a difference in the type of autolysin or in the cell wall structure itself.