LIMULUS, BUTHUS 195 



The Excretory System. — The coxal glands lie one on each 

 side of the endocranium. They may be recognized by their 

 brick-red color. Lobes extend into the bases of the second, 

 third, fourth and fifth pairs of appendages. A duct leads 

 from each of the last pair of lobes, opening on the posterior 

 face of the fifth appendage. 



Cole: Preliminary Dissection of Limulus. Collecting Net, 9, 1934. 

 Lankester: Limulus an Arachnid. Quart. Jour. Mic. Sci., 21, 1881. 

 Packard: The Anatomy, Histology, and Embryology of Limulus poly- 



phemus. Mem. Bost. Soc. Nat. Hist., 1880. 

 Patten and Redenbaugh: Studies on Limulus, Jour. Morph., 16, 1899. 

 Zittel: Text-book of Paleontology. Macmillan and Co., Ltd., 1913. 



BUTHUS (Scorpion) 



Living specimens of these animals are not usually avail- 

 able for laboratory study. They live for the most part con- 

 cealed during the day under old bark and in crevices and 

 holes and are active at night. Their food is largely spiders 

 and insects which are seized by the claws and killed with 

 the abdominal sting. 



1. Into what parts is the body divided? How many seg- 

 ments are recognizable? Which are the most freely movable? 



2. Look for eyes. Do you find any besides the large pair? 



3. Find four pairs of slitlike openings on the ventral side 

 of the pre-abdomen. These are the stigmata, the openings 

 of the lung books. 



4. Find the following appendages: 



(a) The chelicerae. What is their structure and where 

 are they placed? 



(b) The pedipalpi. Compare them with the chelicerae 

 and count their segments. 



(c) Four pairs of walking legs. Count their segments 

 and see if they are armed with claws. 



(d) The comb-shaped pectines. Are they on the thorax 

 or the abdomen? Their function is doubtful. 



5. Examine the mouth. Are there any jaws? Is a labrum 

 present? 



