ABSTRACT
In the last chapter we dealt with the unicellular animals, the protozoa. We chose as our main example Paramecium, and saw that it possesses, in the form of its cilia, many thousands of exactly similar locomotive organs, each of which, when separated from connection with the body, carries out independent motion of a completely stereotyped kind. On the other hand, as long as it is connected in a normal manner with the living cell, it always obeys the unitary impulses proceeding therefrom. In the case also of multicellular animals, the metazoa, we frequently meet with the possession of cilia, which cover, to a greater or lesser extent, the surface or the internal cavities of the body. In smaller forms of metazoa, which live in water, this ciliary coat covering the body frequently serves for locomotion, and we will now see whether, in these cases as well, it is subjected to unitary central impulses.
