46 Invertebrate Zoology. 



The Muscular System. - - How many distinct bands of 

 muscle bundles are there? Their location? Are they seg- 

 mented ? How are the muscles arranged around the acicula ? 



Make a drawing of the muscle bands of six segments, and 

 give special attention to the acicula and their muscles. 



The Reproductive System. The sexes are separate, 

 and the reproductive glands periodically develop from the 

 endothelium of the body-cavity. During the breeding 

 season the eggs, or spermatozoa, often fill, as a granular or 

 creamy mass, many of the chambers of the body-cavity. 

 The eggs are fertilized after extrusion. 



The Excretory System. The external openings of 

 the segmental organs or nephridia have already been noted. 

 By gently displacing the lateral edge of a ventral muscle 

 band, a series of small flask-shaped bodies will be exposed, 

 lying somewhat below the ventral acicula. They are the 

 nephridia. Trace the nephridia anteriorly and posteriorly, 

 and see if they are present in each segment 



Make an enlarged drawing of one of the segmental organs. 



Nervous System. Find the ventral chain of ganglia. 

 Do the ganglia of the several segments occupy the same 

 relative position? Can you find nerves leading from them 

 to the organs or to the body- walls ? Is there anything to 

 show that the ventral chain was originally double? Im- 

 mediately back of the oesophagus, note the enlarged infra- 

 (Ksophageal ganglion. Extending laterally and anteriorly 

 from it are the ocsophageal commissures which unite above 

 the oesophagus in the brain, or siipra-wsophageal ganglion. 

 Do you find nerves passing from the brain, or commissures, 

 to the eyes, tentacles, or palps? 



Make an enlarged drawing of the nervous system. 



