Summary. Whey-proteins in the milk of the grey kangaroo were examined by stairli gel elettrophoresis. Two specific proteins in the whey, altlioiiuli altscnt initially, were produced during the second half of lactation. The production of these proteins was unrelated to the occurrence of oe.strus. ovulation and muting, or to tlie onset of activity in the corpus liiteum derived from ovulation during lactation.INTRODUCTION.