This EM features the infraciliary lattice which forms a continuous network at the level of the proximal ends of basal bodies where the kinetodesmal fibers are connected to the posterior basal bodies of a pair. This system is separated by a small gap from the more superficially located striated bands. The gap has no apparent fibers connecting these two systems. This network forms a highly porous boundary between the ectoplasm and the endoplasm. Electron dense posts are located at each branching site of this network. It is now known that this network is composed of centrin, a contractile protein also found in centrosomes of higher animals including man. TEM taken on 12/18/68 by R. Allen with Philips 300. Neg. 16,000X. Published in J. Cell Biol. 49:1-20, 1971.