Edmund Beecher Wilson (1856 - 1939) was an American geneticist and zoologist. Wilson, is credited as America's first cell biologist, in 1898 he used the similarity in embryos to describe phylogenetic relationships, by observing spinal cleavage in molluscs, flatworms and annelids he concluded that the same organs came from the same group of cells, he concluded that all these organisms must have a common ancestor. He also discovered the chromosomal XY sex-determination system in 1905, Nettie Stevens also described the system in 1905. 1856 was a leap year starting on Tuesday (see link for calendar). ... 1939 was a common year starting on Sunday (link will take you to calendar). ... The United States of America — also referred to as the United States, the U.S.A., the U.S., America, the States, or (archaically) Columbia—is a federal republic of 50 states located primarily in central North America (with the exception of two states: Alaska and Hawaii). ... Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... Zoology (Greek zoon = animal and logos = word) is the biological discipline which involves the study of animals. ... Cell biology (cellular biology) is an academic discipline which studies the physiological properties of cells, as well as their behaviours, interactions, and environment; this is done both on a microscopic and molecular level. ... 1898 was a common year starting on Saturday (see link for calendar). ... Categories: Biology stubs | Developmental biology ... A phylogeny (or phylogenesis) is the origin and evolution of a set of organisms, usually of a species. ... Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... Classes Monogenea Trematoda Cestoda Turbellaria The flatworms (Platyhelminthes, Greek platy: flat; helminth: worm) are a phylum of relatively simple soft-bodied invertebrate animals. ... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata    Oligochaeta - Earthworms and others    Acanthobdellida    Branchiobdellida    Hirudinea - Leeches Class Myzostomida Class Archiannelida (polyphyletic) Class Echiura *Some authors consider the subclasses under Clitellata to be classes The annelids, collectively called Annelida, are a large phylum of animals, comprising the segmented worms, with about... Missing link is a term for a transitional form from the fossil record that connects an earlier species to a later one, or which connects two different species to an earlier ancestor. ... Figure 1: Chromosome. ... The XY sex-determination system is a well-known sex-determination system. ... 1905 was a common year starting on Sunday (see link for calendar). ... Nettie Stevens in 1904 Dr. Nettie Maria Stevens (July 7, 1861 - May 4, 1912) was an early American geneticist. ...

References

• Al-Awqati, Q. 2002. Edmund Beecher Wilson: America's First Cell Biologist (http://www.columbia.edu/cu/alumni/Magazine/Fall2002/Wilson.html). Living Legacies, Columbia University.
• Gilbert, S. F. 2003. Edmund Beecher Wilson and Frank R. Lillie and the relationship between evolution and development (http://www.devbio.com/article.php?ch=23&id=261), Developmental Biology, Seventh edition, Sinauer