Origin and Early Evolution of the Metazoa

Several years ago, we realized that the most prominent ideas that had been ex­ pressed about the origin and early evolution of the Metazoa seemed to have been developed chiefly by zoologists using evidence from modern species without reference to the fossil record. Paleontologists had, in fact, put forth their own ideas but the zoological and the paleontological evidence were about the problem, seldom considered together, especially by zoologists. We believed that the paleon­ tological docu...