Abstract
Summary Mycoplasma possessing characteristics similar to those isolated from mice and described by Sabin have been recovered from lyophilized cultures after 20 years. The type A strain is immunologically related to the L- prototype of Mycoplasma neurolyti-cum and produces, in vitro, a substance capable of inducing rolling disease in mice. The type C strain is serologically unrelated to the type A and L3 strains and appears to have lost its pathogenicity for mice. We wish to acknowledge the valuable assistance of C. Winslow Renshawe.