ABSTRACT
The cortex of Tetrahymena contains a regular array of longitudinal microtubular bands (lms) next to basal body rows running from pole to pole. The lm exhibits a predominant unidirectionality in assembly. The direction of regeneration following breakage of the microtubules is from posterior to anterior of the cell. When the lm and the accompanying basal body row are rotated 180 ° (inverted), so that their polarity is opposite to that of the cell, the predominant direction of regeneration exhibited by the inverted lm is from anterior to posterior. This shows that the lm has an inherent direction of regeneration independent of cellular polarity. This implies that the microtubules constituting the lm have an intrinsic property which controls the direction of assembly. This finding is in accord with the in vitro demonstration using Chlamydomonas flagellar fragments. On the basis of this finding and also the possible pattern of arrangement of the microtubules constituting the lm, it is suggested that growth of the lm involves both elongation of pre-existing microtubules constituting the lm and also laying down of new ones.
Numbering of ciliary rows starts from the mid-ventral row associated with oral morphogenesis and proceeds clockwise around the cell.
Throughout this report, ‘right’ and ‘left’ refer to the right and left of an observer, imagining that he stands inside and lines up antero-posteriorly with the cell and turns around his long axis to face the surface of the cell described. This convention gives a consistent description of the positions of neighbouring organelles on the entire surface of the cell. The terms ‘right-lateral’ and ‘left-lateral’ are used to describe the right and left sides of the cell, respectively, with reference to the ventral oral apparatus.
