ABSTRACT
According to the definition we have given, individuality is not a matter of the indivisibility of the organism, but of the unitary operation, in undisturbed connection, of all the parts. We have hitherto dealt in greater detail with the slipper animalcule (Paramecium), the free-swimming turbellaria, and the starfish. These various animal forms, in themselves entirely different, have this in common, that their locomotion is effected by a large number of similar single organs: in the case of Paramecium and turbellaria, these were the cilia, and in the case of the starfish the suckers. These examples made it particularly evident that the process of locomotion can never be understood from the individual motions alone, but only as a unitary function of the whole. We will now consider animals the bodies of which are built up out of a number of parts which are completely or closely similar in construction, and arranged one behind the other; such animals are the annelids. They are known to everyone by at least one species, the earthworm (Lumbricus).
