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Abstract

As a byproduct of a re-examination of teleost morphogenetic movements, 23 stages in the normal development of salmonid fishes are presented, from fertilization to and beyond hatching, together with rates of their appearance at several constant temperatures. To aid in planning experiments, the period before closure of the germ ring is divided into 13 stages, with detailed discussion of internal structures and movements as well as external features, especially during gastrulation. The literature of salmonid development suggests that the stages are closely applicable to the embryos of any genera of Suborder Salmonoidei. except as to the rates of their appearance. Illustrations are designed for ready identification of stages. Tofacilitate their correlation with the older morphological literature, the principal events of organogenesis in the ectodermal, mesodermal, and endodermal categories are listed according to the stages at which they occur, as determined by dissections and serial sections.