Ascending the scale of life-forms, we next observe the great family of the _Annulosa_, or jointed creatures, which comprises the various families of the worm, the crab, the spider, the ant, etc. In this great family are grouped nearly four-fifths of the known life-forms. Their bodies are well formed and they have nervous systems running along the body and consisting of two thin threads, knotted at different points into ganglia or masses of nerve cells similar to those possessed by the higher animals. They possess eyes and other sense organs, in some cases highly developed. They possess organs, corresponding to the heart, and have a well-developed digestive apparatus. Note this advance in the nutritive organism: the _moneron_ takes its food at any point of its body; the _amoeba_ takes its food by means of its "false-feet," and drives it through its body by a rhythmic movement of its substance; the _polyp_ distributes its food to its various parts by means of the water which it absorbs with the food; the _sea-urchin and star-fish_ distribute their food by canals in their bodies which open directly into the water; in the higher forms of the _annulosa_, the food is distributed by a fluid resembling blood, which carries the nourishment to every part and organ, and which carries away the waste matter, the blood being propelled through the body by a rudimentary heart. The oxygen is distributed by each of these forms in a corresponding way, the higher forms having rudimentary lungs and respiratory organs. Step by step the life-forms are perfected, and the organs necessary to perform certain definite functions are evolved from rudimentary to perfected forms.