TRACHEA TA 



397 



are probably represented by a small rounded plate with a 

 notch in the middle of its border. This bears on its posterior 

 aspect the genital pores. The eighth pair of appendages are 

 termed the pectines; they take the form of an axis, which 

 carries a single row of short processes set like the teeth of a 

 comb ; these are probably tactile in function. The remaining 

 segments in the adult scorpion are devoid of appendages, 

 though there are six more pairs of limbs in the embryo ; but 

 these do not develope, and are lost. 



The third, fourth, fifth, and sixth mesosomatic sterna have 

 each a pair of slit-like openings leading into the lung-books 

 or respiratory organs. These correspond numerically with the 

 last four pairs of branchiae in Limulus. 



The endosternite is a free skeletal plate giving attach- 

 ment to muscles. It lies in the prosoma above the nervous 

 system, and is pierced by a blood-vessel. 



The mouth is extremely minute ; it leads into a small 

 pharyngeal sac with elastic chitinous walls. Certain muscles 



Pig. 226. — Dorsal view of Buthus occitanus, the 

 dorsal integument has been removed to show 

 the digestive organs. From Leuckart, after 

 Blanchard. 



1. Chelicerae. 



2. Oesophagus. 



3. Salivary glands. 



4. Intestine. ' 



5. Liver. 



6. Ducts of liver. 



7. Malpighian tubules. 



8. Intestine. 



act as divaricators of this sac, and thus it functions as a 

 suction-pump, and by its means the scorpion can suck in the 

 juices of its prey, usually spiders or insects. A narrow 



