Experimental Analysis of Developmental Processes in Marine Hydroids

摘要: Hydroids are classical objects of developmental biologists. As early as 1740 the Swiss scientist Abraham Trembley bisected a freshwater polyp. Thus he may be regarded founder experimental biology because subjected animal to regeneration experiment. The first experiment demonstrating what Spemann later termed “organizer principle” was performed by Ethel Browne (1909), about 20 years earlier than work Mangold and Spemann. observed that — upon lateral grafting hydra head into gastric column another secondary axis induced in host. stimulating ideas on possible role gradients control processes also were based observations Hydrozoans (Morgan, 1901, 1905, 1906; Child, 1941). More recently, studies with hydrozoans have once again provided data for further theoretical approaches general mechanism development pattern formation. For instance the, now widely used very instructive, term “positional information” has been coined order describe events occurring body (Wolpert et al., 1971, 1972, 1974).