Ical tele- Two disks of thin metal, or two stretched membranes, each furnished with a mouthpiece, are connected together by a thin string or wire attached at each end to the centres of the membranes.
A good example may be made with two cylindrical tin cups; the bottoms form the membranes and the cups the mouthpieces.
When the connecting string is held taut and sounds, such as those of ordinary speech, are produced in front of one of the membranes, pulses corresponding to the fluctuations of the atmospheric pressure are transmitted along the string and communicated to the other membrane, which in its turn communicates them to the air, thus reproducing the sound.
Free-swimming organisms without cell-membranes exist in both, and from them series of forms can be traced in both directions.
Both cuticularized and suberized membranes are insoluble in cuprammonia, and are colored yellow or brown in a soltition of chlor-iodide of zinc. It is probable that the corky or suberized cells do not contain any cellulose (Gilson, Wisselingh); whilst cuticularized cells are only modified in their outer layers, cellulose inner layers being still recognizable.
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