Advances in the genetics and cell biology of muscle development are discussed. In-vitro analysis of the renaturation, polymerization, and three-dimensional structure of the purified proteins involved is described. (CW)

Discussed are some of the strategies required to try to detect and explain DNA markers that account for small amounts of behavioral variation. Situations in both animal and human behavior are described. The link between molecular biology and behavior is highlighted. (CW)

A rapid sequencing method for ribosomal RNA was applied to the resolution of evolutionary relationships among Metazoa. Describes the four groups (chordates, echinoderms, arthropods, and eucoelomate protostomes) that radiated from the coelomates. (TW)

The evolutionary paths by which the characteristic properties of sex chromosomes may have evolved are reviewed. The evolution of the X and Y chromosomes from a cosexual ancestor is discussed. (CW)

Reports on two longitudinal studies of two-year-old children who were extreme in the display of either behavioral restraint or spontaneity in unfamiliar contexts. Indicates that by age seven most of the restrained group were socially avoidant while the spontaneous children were talkative and interactive. (TW)