Nitrogenous Excretion by Embryos of the Viviparous Snake Thamnophis S. Sirtalis (L.)

1. The garter snake embryo excretes an estimated 2.52 mg. nitrogen, of which 1.4 mg. is recoverable from the embryonic confines. The recovered excreta consist of 16.3% uric acid, 23.4% ammonia and 60.3% urea. 2. The placenta is believed, therefore, to transmit to the mother 1.11 mg. nitrogen per embryo, and it is estimated that it transmits to the embryo approximately 45 mg. of protein as amino-acids. 3. Evidence is presented which suggests that protein may be a principal source of energy, particularly early in development. 4. Growth in terms of wet weight, dry weight, and protein is described.