August Weismann, 1834-1914, was a German evolutionary biologist who contributed to germ-plasm theory. He was born on January 17, 1834 in Frankfurt, Germany. As a child he studied music and collected caterpillars and butterflies, an interest which would later influence his study of the evolution and development of insects. In 1856, Weismann received his medical degree from the University of Göttingen and worked as a physician for several years. In 1863, he joined the faculty of the University of Freiburg, where he taught zoology and comparative anatomy. Weismann first proposed his theory of "germ-plasm" in 1883 after observing insect metamorphosis and the sex cells of various organisms. According to this theory, inherited traits could only be passed down to subsequent generations in a special substance (the germ-plasm) that was found in the germ cells (eggs and sperm). Changes to the rest of the body's cells (somatic cells) were therefore not hereditary. Weismann's theory established him as one of the world's leading biologists and earned him widespread recognition. He died on November 5, 1914.

Antoine Fortuné Marion, 1846-1900, was a French naturalist. He was born on October 10, 1846 in Aix-en-Provence, France. He attended university in Marseille, receiving a degree in arts in 1866 and a degree in science in 1868. His interests included geology, botany, and zoology, especially the study of segmented marine worms and other marine organisms. In 1880 he became the director of the Natural History Museum in Marseilles. He also received several awards and honors from both the French government and the French Academy of Sciences for his research. He died on January 22, 1900.