Edmund Beecher Wilson experimented with Amphioxus (Branchiostoma) embryos in 1892 to identify what caused their cells to differentiate into new types of cells during the process of development. Wilson shook apart the cells at early stages of embryonic development, and he observed the development of the isolated cells. He observed that in the normal development of Amphioxus, all three main types of symmetry, or cleavage patterns observed in embryos, could be found. Wilson proposed a hypothesis that reformed the Mosaic Theory associated with Wilhelm Roux in Germany. Wilson suggested that cells differentiated into other cells when influenced by physiological (dynamic) changes in the hereditary substance contained in cells, and not because of the qualitative division, or parcelling out, of the substance into daughter cells. Wilson published his results in August 1893.

The Cell in Development and Inheritance, by Edmund Beecher Wilson, provided a textbook introduction to cell biology for generations of biologists in the twentieth century. In his book, Wilson integrated information about development, inheritance, chromosomes, organelles, and the structure and functions of cells. First published in 1896, the book started with 371 pages, grew to 483 pages in the second edition that appeared in 1900, and expanded to 1,231 pages by the third and final edition in 1925. Wilson dedicated the book to the cell biologist Theodor Boveri, whose work established the roles of chromosomes in cell division. With its explanations and many illustrations and diagrams, The Cell in Development and Inheritance enabled embryologists to better understand development in terms of cell structure and function.

Petr Kropotkin proposed the theory of Pleistocene ice age, alternative theories of evolution based on embryology, and he advocated anarchist and communist social doctrines in Europe during the nineteenth and twentieth centuries. He traveled in eastern Siberia and Manchuria from 1863 until 1867, and his subsequent publications about that area's geography became authoritative until the middle of the twentieth century. Kropotkin argued that his geographic and geologic observations in Asia, Finland, Sweden, and Canada, supported the theory of Pleistocene continental glaciation, often called the ice age. He was one of the first to study the ancient geography and climate of the Quaternary period, which spans from 2.5 million years ago until the present. Around the turn of the nineteenth century, Kropotkin offered what he said were complementary amendments to Charles Darwin's 1859 theory of evolution by natural selection. Kropotkin employed a variety of arguments from natural history, embryology, and geography to support his theory of mutual aid, which he argued was a positive mechanistic addition to the theory of evolution.

August Friedrich Leopold Weismann studied how the traits of organisms developed and evolved in a variety of organisms, mostly insects and aquatic animals, in Germany in the late nineteenth and early twentieth centuries. Weismann proposed the theory of the continuity of germ-plasm, a theory of heredity. Weismann postulated that germ-plasm was the hereditary material in cells, and parents transmitted to their offspring only the germ-plasm present in germ-cells (sperm and egg cells) rather than somatic or body cells. Weismann also promoted Charles Darwin's 1859 theory of the evolution of species. Weismann argued that only changes to the germ cells, and not body cells, could be inherited, a theory that influenced theories of heredity throughout later centuries.

Walter Stanborough Sutton studied grasshoppers and connected the phenomena of meiosis, segregation, and independent assortment with the chromosomal theory of inheritance in the early twentieth century in the US. Sutton researched chromosomes, then called inheritance mechanisms. He confirmed a theory of Wilhelm Roux, who studied embryos in Breslau, Germany, in the late 1880s, who had argued that chromosomes and heredity were linked. Theodor Boveri, working in Munich, Germany, independently reached similar conclusions about heredity as Sutton. Later scientists named the theory The Sutton-Boveri Theory, or The chromosomal theory of inheritance.

The Inheritance of Acquired Characteristics is a book published in 1924, written by Paul Kammerer, who studied developmental biology in Vienna, Austria, in the early twentieth century. The Inheritance of Acquired Characteristics summarizes Kammerer's experiments, and explains their significance. In his book, Kammerer aims to explain how offspring inherit traits from their parents. Some scholars criticized Kammerer's reports and interpretations, arguing that they were inaccurate and misleading, while others supported Kammerer's work. Kammerer said that the results of his experiments demonstrated that organisms could adapt to different environments by acquiring new features during the course of their lifetimes, and that they transmitted those acquired features to their offspring.

Victor Jollos studied fruit flies and microorganisms in Europe and the US, and he introduced the concept of Dauermodifikationen in the early 1900s. The concept of Dauermodifikationen refers to environmentally-induced traits that are heritable for only a limited number of generations. Some scientists interpreted the results of Jollos's work on Paramecium and Drosophila as
evidence for cytoplasmic inheritance. Jollos was forced to emigrate from Germany to the United States due to anti-semitic government policies in the early 1930s. Nevertheless, his work on Dauermodifikationen remained central to theoretical discourse among German zoologists concerning heredity, development, and evolution.

Eugenical Sterilization in the United States is a 1922 book in which author Harry H. Laughlin argues for the necessity of compulsory sterilization in the United States based on the principles of eugenics. The eugenics movement of the early twentieth century in the US focused on altering the genetic makeup of the US population by regulating immigration and sterilization, and by discouraging interracial procreation, then called miscegenation. Published in December 1922 by the Psychopathic Laboratory of the Municipal Court of Chicago in Chicago, Illinois, the book reports Laughlin's analysis of how states could benefit from sterilizing their mentally disabled residents, and it reprinted his model sterilization law, which he encouraged state governments to adopt. Laughlin's model sterilization law stressed the need for the sterilization of populations that Laughlin deemed inadequate for reasons ranging from physical appearance to socioeconomic status. The document influenced twentieth century legislation in the US about reproduction and compulsory sterilization.

In 1928 Ezra Seymour Gosney founded the non-profit Human Betterment Foundation (HBF) in Pasadena, California to support the research and publication of the personal and social effects of eugenic sterilizations carried out in California. Led by director Gosney and secretary Paul Popenoe, the HBF collected data on thousands of individuals in California who had been involuntarily sterilized under a California state law enacted in 1909. The Foundation's assets were liquidated following Gosney's death in 1942. In 1943, Gosney's daughter donated the remaining assets to the California Institute of Technology (Caltech) in Pasadena, California to establish the Gosney research fund for biological research. Between 1928 and 1942, the HBF published extensively on what they believed to be the benefits of sterilization to both patient and society. The HBF and its members existed within the larger context of the American eugenics movement and scientific institutions, including the Eugenics Record Office at Cold Spring Harbor Laboratory in Cold Spring Harbor, New York, which bolstered the movement's goals of the control of human reproduction and human heredity. Moreover, the model sterilization legislation written by the HBF was disseminated throughout the world to eugenics enthusiasts eager to pass laws limiting the reproduction of people they considered to be unfit.

Edmund Beecher Wilson contributed to cell biology, the study of cells, in the US during the end of the nineteenth and the beginning of the twentieth centuries. His three editions of The Cell in Development and Inheritance (or Heredity) in 1896, 1900, and 1925 introduced generations of students to cell biology. In The Cell, Wilson described the evidence and theories of his time about cells and identified topics for future study. He helped show how each part of the cell works during cell division and in every step of early development of an organism. Developmental biologists trained in the mid-twentieth century reported WilsonÕs text as their foundation for understanding biology, including about how cells, development, heredity, and evolution interact. Wilson considered cells as the center of all biological phenomena.