Stages of Embryonic Development for Alligator sinensis

The embryonic development course of Alligator sinensis was divided into 28 stages,based upon observations on 150 A.sinensis embryos at varied embryonic day,according mainly to their external morphology for early stages of embryos,such as body torsion,brain vesicles,sensory organs morphology,limbs,branchial arches,facial processes,heart,skin and etc,and chiefly to the histological differentiation of their organs for late stages of embryos.It was found that the embryonic day of A.sinensis was relatively in accordance with that of A.mississippiensis for each of early 20 stages and was different for late 8 stages presumably due to a different staging method.It was suggested that histological index about organ differentiation should be introduced into the late stages determination for embryonic development of alligator and crocodiles,so as to make an agreement in staging method and to provide with basic documents and objective references for subsequent studies on developmental biology of alligators and crocodiles.