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. 
