82 ANNELIDA. 



find the nephrostome. Remove a nephridium by means of fine 

 forceps and examine it with a microscope. 



Reproductive System. The sexes are separate, but no per- 

 manent gonads are present. At the breeding season the ova 

 or spermatozoa are proliferated from the coslomic epithelium 

 of a large number of segments and escape by rupture of the 

 body-wall. 



Nervous System. 1 On lifting the alimentary canal you will 

 see the ventral ganglionated nerve cord. Note the nerves pass- 

 ing off laterally from the ganglia. How many pairs of nerves 

 per segment are there, and how are they placed? Are the gan- 

 glia metameric? Is there any indication that the nerve cord is 

 double? At the anterior extremity of the cord note the infra- 

 esophageal ganglia and, extending from them and encircling the 

 anterior end of the alimentary canal, the circum-esophageal con- 

 nectives which unite above in the bilobed brain or supra-eso- 

 phageal ganglia. Sensory nerves connect the brain with the eyes, 

 tentacles, and palps. 



Make a drawing of the nervous system. 



Lillie: Studies of Fertilization in Nereis. I and II. Jour. Morph., 22, 1911. 



III. and IV. Jour. Exp. Zpol., 12, 1912. 

 Mayer: The Annual Breeding-swarm of the Atlantic Palolo. Carnegie 



Inst. Pub., 102, 1908. 

 E. B. Wilson: The Cell-Lineage of Nereis. A Contribution to the Cytology 



of the Annelid Body. Jour. Morph., 6, 1902. 

 Woodworth: The Palolo Worm, Eunice viridis. Bui. Mus. Comp. Zool., 



Harvard, 51, 1907. 



LUMBRICUS. (Earthworm.) 



Earthworms feed mostly at night. What reason is there 

 for this habit? You should look for earthworms with a lantern 

 some mild, calm summer evening when the ground is quite 

 moist. See if they leave their burrows entirely. How much 



1 The nervous system can be most readily studied by tearing it out with 

 needles in a specimen which has been macerated in 20 percent nitric acid 

 for twenty-four hours. Sensory cells and their neurites can be identified 

 in the parapodia by placing them in a 1 percent solution of ammonium 



Eicrate after having let vigorous worms crawl around for three or four 

 ours in a small amount of 1 percent solution of methylen-blue. Mounts 

 of the parapodia should be made in a mixture of glycerin and ammonium 

 picrate solution. 



