A basal body begins its development as a probasal body anterior to
and perpendicularly oriented with the proximal end of a mature basal
body. One or two singlet microtubules first appear in an amorphous
mass of material and this number increases to 9. These singlets become
9 doublets which eventually become 9 triplets. With the lengthening of
the basal body the body begins to tilt upward towards the cell’s
surface and moves away from the mature body. The body penetrates
through the alveolar sac to come in contact with the plasma membrane.
Growth of the cell results in this new basal body taking up its
position in the kinetal row between mature basal bodies. Accessory
structures appear around the new basal body and finally the cilium
develops from the 9 triplets. Published in J. Cell Biol. 40:716-733,
1969. Drawing by H. C. Lyman.
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