In the diagram below,identify the part which connects the peripheral microtubules to the central sheath.

The filament,hook,and basal body are parts of $.........$.

Microtubules were discovered by

Statement $X$ : The cytoskeleton is composed of three types of filaments: microfilaments,microtubules,and intermediate filaments.
Statement $Y$ : Microtubules are hollow tubes made of globular protein tubulin.

Cytoskeleton is made up of

Tubulin protein occurs in