NEREIS VIRENS. 91 



the septum anterior to the body of the nephridium and opens 

 into the ccelomic cavity of the segment next in front, by a 

 cihated funnel, the neyhrostomc . With a hand-lens try to 

 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 coelomic epithelium 

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

 body-wall. 



Nervous System.^ — 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 mfra- 

 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. 



Copeland and Wieman: The Chemical Sense and Feeding Behavior of 



Nereis virens. Biol. Bui., vol. xlvii, No. 4, October, 1924. 

 Just: An Experimental Analysis of Fertilization in Platynereis megalops. 



Biol. BuL, 28, 1915. 

 : Breeding Habits of the Heteronereis Form of Heteronereis megalops 



at Woods Hole. Biol. BuL, 27, 1914. 

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



III. and IV. Jour. Exp. Zool., 12, 1912. V. Jour. Exp. Zool., 14, 1913. 

 Lillie and Just : Breeding Habits of the Heteronereis Form of Nereis lim- 



bata at Woods Hole, Mass. Biol. BuL, 24, 1913. 



* 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 

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

 hours 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. 



