The MBL Embryology Course was instituted in 1893 due to the enthusiastic convictions of a school of leading embryologists that included many of the world’s most important figures in the newly formulated cellular science of developmental biology. A central belief of this school was that the mysteries of the process by which an egg turns into an embryo would yield to a comparative approach, in which underlying commonalities could be sought amongst diverse forms of eggs and embryos. The sea provides the greatest biological diversity with eggs and embryos easily collected in the water. Therefore, almost 130 years ago the MBL was built to facilitate exploration of interesting and illuminating life forms by means of scientific description and experimentation. Evolutionary processes were regarded as an inseparable component of developmental biology, and in extreme cases were used to explain embryonic mechanisms. Even at that early time, development was considered a cellular phenomenon in which the states of cells of different lineages and in different regions of the embryo assume “different values,” (i.e., undergo cellular differentiation). Experimental manipulation of embryonic cells was regarded with great excitement as a means of understanding the developmental origins of differentiated cell lineages. In this scientific environment, the MBL Embryology Course was formulated.
Over a century has now passed, and we have, in many respects, come full circle. Armed with the power of stunning optical, genetic, genomic, molecular, and computing technologies, and mechanistic concepts, the field of early development is now providing scientific answers to the developmental questions first formulated between 1885 and 1915. Once again, comparative analyses have emerged as interesting and important facets of developmental studies. At the molecular level, evolutionary considerations have become of enormous interest to investigators concerned with embryonic gene regulation. Rather than a reductionist view, early development is again conceived of as a problem that must be considered in terms of what embryonic cells actually do. In the intervening century, the field of Embryology (and no doubt the Embryology Course per se) was subject to a number of strong ideological currents, many of which in retrospect seem exaggerated or erroneous in orientation. Genetic approaches were, until relatively recently, separated almost entirely from the rest of embryology. The impressive demonstration of Spemann’s “organizing centers” and “embryonic fields” set off an essentially non-cellular and also non-molecular form of experimental phenomenology that lasted for decades. In the 1960s the importance of the genome began to be reconsidered in embryological investigations, and a new phase in the discipline emerged in which molecular biology, genetics, and embryology were meld together. When applied to the enormous wealth of classical embryological information, the complexity of the resulting brew discouraged many of the new practitioners, who then sought refuge within single biological systems, single technologies, and experimental approaches, or single levels of analysis. Only in recent years have we found sufficiently sophisticated paradigms so that it is now profitable and useful to consider all kinds of embryos, and all kinds of early developmental processes at all levels of biological organization, within the same conceptual framework.
Such rich history leads to a clear enunciation of the irreplaceable role that the Embryology Course continues to play in the new millennium. More so now than ever, the Embryology Course has become a vehicle for presenting, at the most advanced level, a unified conceptual framework, within which the problem of how eggs generate embryos can be considered mechanistically and comparatively, in genetic, epigenetic, molecular, cellular, morphogenetic, and evolutionary terms.