No abstract

No abstract

No abstract

Moore ( '41) has shown that the hybrids of different species of Rana will develop normally to a certain stage of development and then stop at this stage for a period of time without further differentiation. These arrested eggs provide an opportunity f o r an analysis of the concomitant changes in metabolism and promise to help elucidate the relation between metabolism and development.The pipiens egg X sylvatica sperm hybrid develops at the normal pipiens rate up to the formation of a clear dorsal lip of the blastopore stage 10 (Pollister and Moore, '37; Shumway, '40). Following this there is relatively little change in the blastopore lip although there may be some cellular rearrangements such that the yolk area becomes smaller. Moore ('46) has described these movements in detail. These "gastrulas" remain healthy until the hatching of the normal pipiens embryos (stage 20) after which the hybrids soon undergo cytolysis. During the intervening period they increase greatly in diameter, become ciliated and finally shrink back to their original size. (For details of development see Moore, '46.)The following experiments were planned in accordance with the assumption that morphological processes, such as gastrulation, are dependent upon the energy produced from