TRACHEATA 39 
N 
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 les 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 chitimous walls. Certain muscles 
Fic. 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. 
i 
Malpighian tubules. 
ao 
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 
