If the protoplasm contains visible granules, as it usually does, within a clear external layer, we see that these stream constantly forwards along the central axis of each process as it forms, and backwards just within the clear layer all round, like a fountain playing in a bell-jar. This motion is most marked when a new pseudopodium is put forth, and ceases when it has attained full dimensions.
We use as a corresponding adjective the term "plasmic."
For the study of the structure of protoplasm under the microscope it is necessary to examine it in very thin layers, such as can for the most part be obtained only by mechanical methods (section-cutting, etc.). These methods, again, can only be applied to fixed specimens, for natural death is followed by rapid changes, and notably by softening, which makes the tissue less suitable for our methods. We further bring out and make obvious pre-existing differentiations of our specimens by various methods of staining with such dyes as logwood and cochineal and their derivatives, and coal-tar pigments (see also p. [11] n.).
In many Protista these granules have been shown by Schewiakoff, in Z. wiss. Zool. lvii. 1893, p. 32, to consist of a calcium phosphate, probably Ca3P2O8.
It is not always possible to tell how much of these structures represents what existed in life (see p. [11]).