German-American biologist. Loeb was one of the earliest and most prominent Jewish biologists in the United States. Loeb's initial work, before he emigrated to the U.S. in 1891, extended Sachs' theory of tropisms from plants to animals, showing that the movements of simple animals were determined by light, gravity, etc. Loeb was best known for his work (following Roux) showing that echinoderm larvae could be chemically stimulated to develop in the absence of fertilization. This was widely celebrated as showing that science would eventually come to control the fundamental processes of biology. However, Loeb's results were challenged by Lillie and Just after Loeb moved on to protein chemistry in the 1920's. Quickly accepted Mendelian genetics after the turn of the century and did some work on mutation, but did not vigorously pursue research in that area. Friend of Wheeler. Loeb's brother Leo was a successful pathologist.