The biochemistry and assembly of ciliary, flagellar, and mitotic microtubules will be investigated by three approaches. The subunits of tubulin heterodimers from axonemal outer doublet subfibers and central pair and from mitotic apparatus microtubules will be compared on the basis of cyanogen bromide and tryptic peptide mapping, end group and amino acid analyses, and immunological similarity; primary structural variation will be correlated with tubule stability and function. The chemistry of the mitotic apparatus will be investigated by a comparative biochemical and ultrastructural study under various isolation conditions, through in vitro reactivation, and by thermodynamic analysis of spindle equilibrium during experimental modification of total and local spindle protein pool. The association of microtubules and the assembly of axonemes will be studied in vitro by reassociation of fractionated tubulins, dynein, and architectural proteins upon basal body templates and in vivo by pulse-labeling of enzymatic and structural proteins of sea urchin blastula cilia to follow sequential and quantal synthesis and their correlation with morphological events.