The study of dipterous embryology dates back to Kölliker (1843)when he made the first observations on Diptera which had any bearing on embryology. Kölliker no doubt saw the blastoderm on the surface of the egg. Weismann's outstanding work on the development of the fly in the egg appeared in 1863–64. It was Kowalevsky who revolutionized research in insect embryology in 1871, first using the methods of microscopic anatomy and so initiating the period of modern research in the field. He studied the development of a large number of insects and discovered their germinal layers. The most extensive of all work on dipterous embryology is that of Graber (1879, 1888, 1889, 1890) in which he covers nearly the whole ground of the muscid embryological development, beginning with cleavage and concluding with a description of the nervous system and formation of the imaginal discs. Graber made comparisons of the embryology of various insects and studied especially Lucilia caesar L. and Calliphora vomitoria. Gambrell (1933)lists Diptera which have been studied embryo-logically up to 1932.