I20 ANIMALS 



94. Annelida: 



(a) If living Nereis is at hand study its movements. 



(b) In a dorsal view of Nereis note general form of body; head; sen- 

 sory, locomotor, and respiratory appendages; segmentation; 

 symmetry. 



(c) In a small living specimen the dorsal blood vessel may be seen. 

 Note its rhythmical contractions. Note the direction of the 

 flow. 



(d) Study the head with a lens. Note the proboscis, tentacles, palps, 

 cirri and eyes. 



(e) Study a segment cut from the middle of the body. Note the 

 four large muscle masses, the intestine, the body cavity, the 

 dorsal and ventral blood vessels, the ventral nerve cord and the 

 parapodia. 



(f) On a parapodium note its two divisions — dorsal and ventral 

 rami — each bearing a cirrus, a ligula, setigerous lobes, setae and 

 an aciculum. 



(g) In a portion of the body from which the dorsal wall has been 

 removed, note the intestine, the body cavity and the mesenteries. 



(h) In a microscopic preparation study the ova. 



95. Compare the earthworm (Lumbricus) with Nereis. 



96. Some of the smaller fresh-water annelids may be studied living, as 

 transparent objects, under the microscope. 



97. Arthropoda: 



(a) If living crawfish (Cambarus) or lobsters (Homarus) are available 

 study the movements. Note how the tail fin is used in loco- 

 motion, also the legs. By adding a little carmine to the water 

 can you detect any respiratory currents? What causes them? 

 Feed with an earthworm and note activity of sense organs and 

 the method of ingestion of food. 



(b) In a dorsal view note type of symmetry and character of seg- 

 mentation of the body. 



(c) In a lateral view note in the cephalothorax: rostrum, head, nuchal 

 groove, thorax. In the abdomen: segments (No. ?), telson. The 

 appendages of the cephalothorax are: i antennules, 2 antennae, 

 (eyes), 3 mandibles, 4 first maxillae, 5 second maxillae, 6 first 

 maxillipeds, 7 second maxillipeds, 8 third maxillipeds. (For 

 appendages 3 to 8 see d). 9 Chelae, 10-13 ambulatory appen- 

 dages. Are these all alike? The appendages of the abdomen 

 are: 14-18 pleopods, 19 uropods. Are the pleopods all alike? 



