THE RISE OF FISH EMBRYOLOGY IN THE 19TH-CENTURY

SYNOPSIS, The nineteenth century was critical for the empirical and co nceptual growth of developmental biology, Fishes played a central role in this process, The study of fish development, mainly that of teleos ts but also chondrichthyans, can be traced back to classical times, In the nineteenth century, it merged with modern descriptive embryology, continued with the rise of comparative embryology associated with evo lutionary studies, and moved into the experimental and physiological a nalysis of development, Any consideration of fish development must tak e into account that fishes phylogenetically are the most diverse group of the vertebrates and also the most speciose, These features are ref lected in the diversity of their development, The descriptive embryolo gy of fishes is reviewed from Aristotle to the beginning of the ninete enth century. The study of chondrichthyans, especially viviparous spec ies, was characteristic of this period, During the nineteenth century, there was a progressive development of knowledge of the descriptive e mbryology of teleosts and chondrichthyans. Teleosts came to the fore b ecause artificial fertilization ensured a ready supply of material and their transparent eggs were well suited for microscopy, The subsequen t development of embryological microtechnique made possible the examin ation of sectioned material and moved research to a more cellular leve l. By the end of the century, an in-depth description of development w as in place, Interest in the comparative embryology of fishes was stim ulated by Haeckel's melding of embryology and evolution and led to a d escription of development of agnaths, chimaeras, lungfish, and primiti ve actinopterygian fishes, Experimental and analytical methods of inqu iry began to be used at mid-century, The experiments of Ransom on the contractility of egg cytoplasm, Lereboullet's experimental teratology, chemical studies of embryonic nutrition in viviparous fishes, in vitr o observation of blastomeres, His's concrescence theory of embryo form ation and Kastschenko's and Morgan's testing of it are considered.