INTEENAL ANATOMY. 125 



of which reaches beyond the sub-oesophageal ganglion, 

 and lies under the posterior part of the oesophagus ; 

 whatever its form or size it serves as a skeletal piece 

 whence arise, inter alia, the depressor muscles of the 

 coxa3 (PL C, fig. 3, mdc). 



The levators and depressors are not the only muscles 

 inserted into the coxge ; these joints are capable of 

 considerable lateral and rotatory motion, which is 

 effected by short muscles arising from the sternum and 

 from the epimera ; in Rhizoglyphus echinopus the first 

 pair of coxae, which are the most moveable, have some 

 of these muscles arising from each of those sclerites. 



The flexor muscles which move the respective joints 

 of the leg arise, as is the case in most but not in quite 

 all Acari, from the cuticle ; principally from the dorsal 

 part of the cuticle ; not of the joint next to the one 

 raised, but of the second joint more proximal than that 

 moved ; thus the muscles moving the tarsus arise from 

 the genual, not from the tibia ; they are almost always 

 inserted into the proximal edge of the joint moved. 



One result of these arrangements is that each joint 

 of the legs, except the terminal ones, contains parts of 

 at least two sets of muscles. Nalepa states that in 

 Carpocjlyplius the same remark is applicable to the 

 coxa ; he says that as there is not any joint more 

 proximal than the coxa, the muscles which move the 

 femur arise in the body from the epimera. 



The extensor muscles, which are much smaller than 

 the flexors, arise chiefly from the immediately previous 

 joint. 



The extensor muscle of the claw arises from the 

 proximal edge of the tarsus ; its tendon is long and is 

 inserted into the dorsal side of the claw (PL C, fig. 7). 

 Nalepa says that in Carpoglyplius the flexor of the claw 

 arises from the tibia, passes through the tarsus, and is 

 inserted by a short tendon into the under side of the 

 claw. 



Nalepa also states that in Carpoglyphus there is an 

 auxiliary tarsal-flexor arising from the tibia. 



