LEPAS, LIMULUS 189 



prolongation which extends to near the bases of the abdominal 

 appendages. On the margin of this prolongation are the 

 small scalelike mandibles, first maxillae, and second maxillae. 

 The stomach 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 need 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. An 

 ovigerous mass may sometimes be found lying between the 

 body and mantle. Remove some of this, place on a slide, 

 cover, and examine with the compound microscope. 



7. Examine the appendages carefully and be sure that 

 you understand the relation of parts. Remove the thoracic 

 appendages one by one on one side only. What part must 

 the peduncle represent? Note the beautiful adaptation of the 

 animal for its life. 



A drawing showing the organs is desirable. 



Bigelow: Early Development of Lepas. Bull. Mus. Comp. Zool. Har- 

 vard, 40, 1902. 



Delage: Evolution de la Sacculine. (Sacculina carcini.) Arch. Zool. 

 Exp. et Gen., 2 e Series, 11, 1884. 



ARACHNIDA 



LIMULUS (Horseshoe Crab) 



Notice the way in which the animal crawls upon the bot- 

 tom. Is it well protected from enemies? Examine it care- 

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

 Disturb it and see if it will swim. The animals are usually 



