vi PRACTICAL DIRECTIONS 359 



the lateral half of your section, and then put on the high 

 power and work through 1-7 again. Notice that the 

 cavities in the sections of the nephridia are intra-celhdar, 

 except in the muscular part (p. 341). Sketch as many 

 details as possible. 



Sift some earth and look for cocoons. 



NEREIS 



Note : i. The head, consisting of (a) prostomium with 

 its tentacles, palps, and eyes, and (b) perisi&mium with its 

 tentacles; also the proboscis, month, and lateral chitinous 

 jaws. 



2. The metameres of the body, each with a pair of 

 (a) dorsal and ventral cirri, and (b) lobed parapods, each sub- 

 divided into notopod and neuropod, and bearing a bundle of 

 chitinous seta. 



3. The anal segment with anal cirri, but no parapods. 

 Carefully cut out an entire parapod and mount it on a 



slide (Fig. 88). Note the two bundles of setce, each made up 

 of an aciculum and of numerous jointed seta; of two different 

 forms. The structure of the seta; will be more easily made 

 out if separated from one another with needles, or if the 

 entire parapod is treated with a solution made by dissolving 

 5 grammes of potassium hydrate in 100 c.c. of water. 



Prepare sections, in the usual way, of the prostomium, 

 passing through the eyes, and note the pigmented optic cup 

 and retina, the pupil, and lens. 



Procure some trochospherc larva? (see note on p. 325). 

 Mount and compare with Fig. 89. 



