摘要：

The spindle trichocysts of Paramecium caudatum were examined by means of the freeze-fracture technique. The A-face of the greater part of the trichocyst membrane possesses randomly distributed 10-nm diameter particles which are present in a frequency of about 800 particles/ μm 2. The B-face shows the same number of corresponding depressions. The membrane surrounding the distal one-third of the trichocyst tip is encased within a tubular collar. This external specialization of the trichocyst membrane is complemented in the same area of the membrane by an intramembranous differentiation; that is, the A-face and the B-face are, respectively, free of particles and depressions. The particles with a circular profile, which were in this area during trichocyst development, are now concentrated within the trichocyst membrane at its distal tip. Rows of oval particles that appear on the A-face of the unfixed-frozen trichocyst membrane after collar formation show that this existing membrane has undergone a process of differentiation.

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