66 INVERTEBRATE ZOOLOGY 



system from the body, mount it in glycerine, and study it 

 under a microscope. Note the ganglionic enlargements and the 

 double nature of the nerve cord. Study the branches which 

 pass off from the nerve cord and from the brain. 



Exercise 9. Draw the nervous system on a scale of 10, showing 

 all the features above mentioned. 



The reproductive system. There is no complicated reproductive 

 system in Nereis. The sexes are separate. The reproductive 

 glands make their appearance only during the periods of sexual 

 activity and then as swellings of the peritoneal lining of the 

 body-cavity. The eggs or spermatozoa, as the case may be, 

 fall into the body-cavity and find their way to the outside 

 through the nephridia or through temporary openings in the 

 body-wall. 



Exercise 10. Draw a diagram representing an ideal cross section 

 in the region of the stomach-intestine ; show the stomach- 

 intestine with its mesenteries, the blood vessels, the nerves, 

 and the muscles. 



