  Every organism has a size that is convenient for its function. Not only
multicellular organisms but also uni-cellular organisms and even subcellular
structures have convenient sizes. Flagella of eukaryotic cells are long dynamic
cell protrusions. Because of their simple linear geometry, these cell
appendages have been popular system for experimental investigation of the
mechanisms of size control of organelles of eukaryotic cells. In the past most
of the attention have been focussed on mono-flagellates and bi-flagellates. By
extending our earlier model of bi-flagellates, here we develop a theoretical
model for flagellar length control in {\it Giardia} which is an
octo-flagellate. It has four pairs of flagella of four different lengths.
Analyzing our model we predict the different sizes of the four pairs of
flagella . This analysis not only provide insight into the physical origins of
the different lengths but the predicted lengths are also consistent with the
experimental data.
