1. The respiration of phosphate-buffered cell-free homogenates made from R. pipiens embryos increases exponentially with the age of the embryos up until the time at which they are in the tailbud stage, after which the rate declines.2. Addition of 0.2% sodium deoxycholate elevates the respiration of homogenized embryos at any pre-tailbud stage to that of tailbud-breis, but has no effect upon that of breis of post-tailbud embryos.3. The respiration of plain- or deoxycholate-treated breis is at all stages greater than or equal to that of intact embryos.4. The respiration of breis (plain- and deoxycholate-treated) made from gastrula-arrested R. pipiens ♀ x R. sylvatica ♂ hybrid embryos is at all non-moribund stages quantitatively the same as that of control breis of normal embryos.5. The implications of these findings are briefly discussed.