A detailed analysis of the decays in Right of negative E' mesons and hyperons, obtained with the 48-in. cloud chambers in Pasadena, is presented. The principal results are the following:1.Two new fully measurable~events add to the already strong evidence for the existence of this particle.2. E' events with a single charged secondary are shown to be most consistent with the E 2 and E"'2 decay modes.3. An analysis of 7 Caltech events is shown to lead to a Q value of 65%3 Mev, and a 50/0 con6dence lower limit to the lifetime of 4.6)&10 ' sec. A rough upper limit to the lifetime of