Examine a live specimen placed on moist paper or wood. Note the characteristics of its locomotion, and the movements of its body-parts. How do the setæ aid in locomotion?

Internal structure (figs. [25], [26] and [28]).—Technical Note.—With a fine-pointed pair of scissors make a dorsal median incision, not too deep, behind the clitellum and cut forward as far as the first segment. Put the specimen into dissecting-dish, carefully pin back the edges of the cut and cover with clear water or, better, 50% alcohol.

Note the long body-cavity divided by the thin septa which have been torn away for the most part by the pinning process. Note the thin transparent covering of the body, the cuticle. Just beneath this note a less transparent layer, the epidermis, and underneath this a layer of muscles. The muscular layer is made up of two clearly recognizable sets, an outer circular layer and an inner longitudinal layer the fibres of which are continuous with the septa.

Note, as the most conspicuous internal organ, the long alimentary canal, of which a number of distinct parts may be recognized. Most anteriorly is a muscular pharynx, which is followed by a narrow œsophagus, leading directly into the thin-walled crop; next comes the muscular gizzard, and next the intestine which opens externally in the terminal segment through the anus. The anterior end of the alimentary canal is more or less protrusible, while the posterior portion is held more firmly in place by the septa which act as mesenteries. Surrounding the narrow œsophagus are the reproductive organs, three pairs of large white bodies and two pairs of smaller sacs.

Note the dorsal blood-vessel lying along the dorsal surface of the alimentary canal, from the anterior portion of which arise several circumœsophageal rings or "hearts." These hearts are contractile and serve to keep the blood in motion through the blood-vessels (see later). In the most anterior of the body segments note the pear-shaped brain or cerebral ganglion.

Technical Note.—Lift carefully to right and left the reproductive organs, thus exposing the œsophagus.

Note three pairs of bag-like structures projecting from the œsophagus. The front pair is the œsophageal pouches; the next two pairs are the œsophageal or calciferous glands. They communicate with the alimentary canal, and their secretion is a milky calcareous fluid.

Make a drawing that will show all the parts so far studied.

Technical Note.—Cut transversely through the alimentary canal in the region of the clitellum and carefully dissect the anterior portion of the canal away from the surrounding organs.

Note the dorsal fold of the intestine, typhlosole, extending into the lumen. This fold gives a greater surface for digestion, and in it are a great many hepatic or special digestive cells. The entire alimentary canal is lined with epithelium. Observe just beneath the alimentary canal the ventral blood-vessel, and still beneath this blood-vessel the ventral nerve-cord. There is a slight swelling on the nerve-cord in each segment of the body. These swellings are the ganglia. How many pairs of nerves are given off from each ganglion? Observe in each segment, posterior to the first three or four, the successive pairs of convoluted tubes, the nephridia, or organs of excretion. Each nephridium opens internally through a ciliated funnel, the nephrostome, within the body-cavity, while it opens externally by a small excretory pore between the setæ on the ventral surface of the segment behind that in which the nephridium chiefly lies. The function of the nephridia is to carry off waste matter from the fluid which fills the body-cavity.