Stages in the Normal Development of the Common Garter Snake, Thamnophis sirtalis sirtalis

published part I of his great monograph on the development of the viper in 1903, but it only goes as far as the closure of the amnion, and part II was not completed before his death in 1936. Little has been published on older stages. Parker (1878) noted six stages of skull formation, and Berchelt (1936) described six other stages in the differentiation of the hemipenis. Franklin (1945) recorded the ages and lengths of 25 stages in the development of Natrix taxispilota, but these stages are not defined anatomically. Few complete series of snake embryos are known to exist in research collections. It is