The Rise of Fish Embryology in the Nineteenth Century

Abstract

SYNOPSIS. The nineteenth century was critical for the empirical and conceptual growth of developmental biology. Fishes played a central role in this process. The study of fish development, mainly that of teleosts 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 evolutionary studies, and moved into the experimental and physiological analysis of development. Any consideration of fish development must take into account that fishes phylogenetically are the most diverse group of the vertebrates and also the most speciose. These features are reflected in the diversity of their development. The descriptive embryology of fishes is reviewed from Aristotle to the beginning of the nineteenth century. The study of chondrichthyans, especially viviparous species, was characteristic of this period. During the nineteenth century, there was a progressive development of knowledge of the descriptive embryology of teleosts and chondrichthyans. Teleosts came to the fore because artificial fertilization ensured a ready supply of material and their transparent eggs were well suited for microscopy. The subsequent development of embryological microtechnique made possible the examination of sectioned material and moved research to a more cellular level. By the end of the century, an in-depth description of development was in place. Interest in the comparative embryology of fishes was stimulated by Haeckel's melding of embryology and evolution and led to a description of development of agnaths, chimaeras, lungfish, and primitive actinopterygian fishes. Experimental and analytical methods of inquiry 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 vitro observation of blastomeres, His's concrescence theory of embryo formation and Kastschenko's and Morgan's testing of it are considered.