LIMULUS 193 



part of the cephalothorax. If this organ be pushed to one 

 side it is possible to see the esophagus leading from the 

 mouth forward to the under side of the stomach. Turning 

 now to the more posterior parts of the digestive tube, it will 

 be seen that the stomach leads directly into the long, straight 

 intestine. The latter ends in a muscular rectum, which opens 

 to the exterior through the anus. If the esophagus, stomach 

 and pyloric valve be split open, the strongly ridged chitinous 

 lining may be seen. The intestine, on the other hand, has a 

 glandular lining. On each side of the intestine may be found 

 a pair of hepatic ducts which convey fluids from the liver to 

 the lumen of the intestine. 



The Nervous System. — Sever the digestive tube at the 

 rectum and again at the junction of the esophagus and 

 stomach. Carefully remove this section of the tube. The 

 endocranium (a cartilaginous shelf supposed to be homol- 

 ogous with the cartilaginous brain case of certain verte- 

 brates) is in clear view. This should be removed carefully 

 to expose the underlying brain or nerve collar. The esopha- 

 gus is completely encircled by the brain. Note an anterior 

 enlargement, the frontal lobe or forebrain. Three olfactory 

 nerves and a nerve to the median eye are given off from its 

 anterior end. Arising from the hemal surface of the fore- 

 brain are a pair of lateral eye nerves and a pair of smaller 

 lateral or first hemal nerves. Behind the latter are seven 

 pairs of hemal nerves radiating from the nerve ring. A 

 pair of stomodeal nerves arise from the inner anterior edge 

 of the nerve ring. 



The nerves so far described are those the origins of which 

 may be seen when the brain is in situ. All nerves should be 

 fully exposed and traced to the organs which they supply. 

 Schaudinn's fluid may be used to whiten the nervous tissue. 

 (Note: this solution is poisonous.) 



It is desirable to draw the nervous system- in situ. 



Further study of the nervous system may be made by 

 removing the brain and nerve cord. To remove the brain and 

 13 



