1890
	The numerical equality of paternal and maternal chromosomes at fertilization was established by Theodor Boveri in Germany and Jean-Louis-Léon Guignard in France.	1890
		1891
	Publication of August Weismann's book Das Keimplasma (The Germ Plasm) emphasized meiosis as an exact mechanism of chromosome distribution.	1892
		1893	Grover Cleveland becomes twenty-fourth president of the United States.
	Hans Dreisch expounded the view that all nuclei of an organism were equipotential but varied in their activity in accordance with the differentiation of tissues. William Bateson's Materials for the Study of Variation emphasized the importance of discontinuous variations, foreshadowing the rediscovery of Mendel's work. Karl Pearson published the first in a long series of contributions to the mathematical theory of evolution. Methods for analyzing statistical frequency distributions were developed in detail.	1894
	Wilhelm Konrad Röntgen (Roentgen) discovered x-rays, which were soon to be applied in the visualization of bodily structures and in the induction of genetic mutations (both intentionally and accidentally).	1895	The Lumiere Brothers introduce moving pictures.
	E. B. Wilson publishes The Cell in Development and Heredity. This influential treatise (ultimately reprinted in several editions) distills the information compliled concerning cytology in the half-century since Schleiden and Schwann put forth the cell theory.	1896
	Gabriel Bertrand coined the term COENZYME to designate inorganic substances which were necessary to activate certain enzymes.	1897	William McKinley becomes twenty-fifth president of the United States.
		1898
	The First International Congress of Genetics held in London. Richard Altmann renamed "nuclein" NUCLEIC ACID. William Bateson writes a paper on hybridisation and cross-breeding as a method of scientific investigation that anticipates Mendel's rediscovery.	1899
		1900