Algae exhibit the greatest variety of cell motility phenomena in the living world. These range from the peculiar gliding motility of filamentous blue green algae or cyanobacteria to chloroplast movements and cytoplasmic streaming which are most common in higher plants. In addition, cell motility by eukaryotic flagella is the characteristic mode of cell locomotion in algal flagellates and most reproductive cells of algae. Algae use these cell motility systems mainly to orient themselves or their photosynthetic organelles in a suitable light gradient to optimize growth and reproduction. In consequence most of the motility systems are coupled to photoreceptors and are regulated by signal transduction cascades. Algal cell motility has thus attracted consid erable interest also from non-phycologists and some algal motility systems have become models of research in cell and molecular biology. This book summarizes some of the progress that has been made in recent years in the analysis of cell motility phenomena in the algae. Although complete coverage of the subject was not attempted, the six chapters cover all the major types of cell motility systems and the authors provide in depth reviews of gliding motility, chloroplast movements, cytoplasmic streaming, flagellar beat pat terns, mechanisms of flagellar movement and centrin-mediated cell motility."

Protists are fascinating organisms that have diversified and protozoologists. For example, phycologists use the evolutionarily to inhabit most of the biosphere. Their term "basal body" while protozoologists use "kine- tosome"; mycologists were indifferent and used both cytoskeleton is the primary reason that such a diver- sification is possible. Microtubules provided freedom terms! from the constraint of prokaryotic cell walls and they As knowledge increased, it became more and more were organized in various cytoskeletal configurations. apparent that the organisms studied in the classical The nine pairs plus two flagellum, a major component fields did not fit into monophyletic lineages. And when of many protistan cytoskeletons, gave a new meaning efforts were made to organize the protists into a phy- to the word motility beginning at least one thousand logenetic classification, it became strikingly apparent million years ago. Associated with the development of that we needed a common vocabulary. Until such a the flagellum were new contractile and noncontractile common vocabulary exists, it will remain difficult to proteins that are necessary for control and manipu- compare studies by scientists from different fields, it lation of the flagella. As the new protists ventured out will be difficult to identify homologous structures into new habitats and filled new niches, they evolved among protists, and the historical barriers created by new ways of sensing their surrounding environment. individual fields of mycology, phycology and proto- Phototactic responses became tightly coupled with the zoology will remain.