LIMULUS. 147 



of the peduncle are the scuta, and near the extremity the terga. 

 Why are there so many pieces ? Notice the lines of growth and 

 determine the direction of growth of each piece. 



Draw the animal as seen from one side. 



With a scalpel or razor cut a preserved specimen into right 

 and left halves, extending the cut through the peduncle. 



4. The mouth will be seen at the end of a rather thick pro- 

 longation which is extended to near the bases of the abdominal 

 appendages. On the margin of this prolongation are the small 

 scale-like mandibles, first maxillce, and second maxillae. The sto- 

 mach is rather large and the small intestine leads to the posterior 

 end of the abdomen, where it opens between the abdominal 

 appendages. 



5. The nervous system, consisting of a large pair of cerebral 

 ganglia and a short ventral chain of ganglia, should be seen in 

 such a section. 



6. The animal is hermaphroditic. The testes lie dorsal to 

 the stomach and communicate with a conspicuous coiled vas 

 deferens that is continued to the elongated penis at the end of the 

 abdomen. What reason is there for such a long penis? The 

 ovary occupies the interior of the peduncle. The oviducts are 

 inconspicuous and hard to follow. They open near the bases 

 of the anterior thoracic appendages. 



7. Examine the appendages carefully and be sure that you 

 understand the relation of parts. What part must the pedun- 

 cle represent? Understand the beautiful adaptation of the 

 animal for its life. 



A drawing showing the organs is desirable. 



ARACHNOIDEA. 



LIMULUS. (Horseshoe Crab.) 



Notice the way in which the animal crawls upon the bottom. 

 Is it well protected from enemies? Examine it carefully for 

 parasites and for animals that are attached to it. Disturb it 

 and see if it will swim. The animals are usually quite active 



