First signals : the evolution of multicellular development /

First Signals discusses themes that permeate Bonner's seven other books: the origins of multicellularity and embryonic development, the evolution of development, cellular metabolism, cell-to-cell signaling, and the biological significance of size, shape, and polarity. Multicellularity and its origins are used to probe how development in multicellular organisms arose. In clear, crisp writing, Bonner discusses examples from many multicellular organisms, especially cellular slime molds. Multicellularity arose many times, normally by fusion of cells or by failure of cells to separate. Bonner discusses why multicellular animals and plants must maintain a unicellular reproductive stage in parallel with a multicellular embryo--multicellularity as a compromise among reproduction, generation, inheritance, and variation. A chapter is devoted to selection for increase and decrease in size. The origins of multicellularity are discussed in the context of the evolution of replication, the birth of metabolism, and the development of a stimulus response system--the signals and receptors that allow cells to associate rather than separate. The origins of cell differentiation are related to mechanisms of gene expression. Discussions of polarity, patterning, and the use of mathematical models complete the book. All levels. B. K. Hall Dalhousie University