The King Crab. 117 



immediately under the stomach, the cartilaginous sternal 

 plate. Note the outline of the plate and remove it with 

 care, as a portion of the nervous system lies immediately 

 beneath. 



The nervous system consists of a brain, a circum-oral ring, 

 and a ventral, posterior continuation, the ventral cord. The 

 brain is a rounded body lying in front of the oesophagus. 

 Trace the nerves leading from it. The circum-oral ring is 

 a flattened disc which innervates the ambulatory appen- 

 dages. The posterior part of the ventral cord gives off 

 branches to the abdominal appendages. The more central 

 portions of the nervous system are surrounded by a blood- 

 sinus. 



Make a drawing of the nervous system. 



