574 CutnH PING 
to the intersegmental ring of the third and fourth segments, while the 
ventral pairs are attached, one to the caudal end of the dorsal process 
of the pharyngeal plate, and the other to the ventral. They are stomal 
dilators. The pharyngeal depressors are the pair of muscles situated 
dorsal to all the others. They have one end attached to the intersegmental 
ring between segments 3 and 4, and the other end inserted on the 
posterior end of the dorsal side of the pharyngeal mass. There are two 
pairs of cephalopharyngeal protectors, one dorsal and one ventral. These 
are attached to the third segment of both the dorsal and the ventral side, 
respectively. Their other ends at each side are inserted together on the 
dorso-lateral region of the posterior end of the pharyngeal mass. Six 
pairs of cephalic retractors are inserted into the cephalic ring between 
the first and the second segment. The three dorsal pairs are attached to 
the posterior end of the fourth segment, while the three ventral pairs, 
attached to the same segment, are slightly cephalad in position. 
Within the pharyngeal mass there are two sets of muscles, which are 
best seen in sections. One set is longitudinal. Hewitt, in the Musca 
larva, calls them the oblique pharyngeal muscles, because their ventral 
attachment is posterior to the dorsal attachment. These muscles are 
attached dorsally to the inside of the dorsal ridges of the lateral plate and 
ventrally to the roof of the pharynx. The other set is best seen in the 
caudal region of the pharynx. They lie horizontally over the pharyngeal 
cavity, and are called by Hewitt the semicircular pharyngeal muscles 
(Plate LV, 20). 
The cutaneous muscles— On the inner side of the dorsal body wall, 
two pairs of the dorsal longitudinal muscles are found, lying on both sides 
of the median line. They are arranged according to the body segments. 
On the ventral side there are three pairs of ventral longitudinal muscles. 
Both the dorsal and the ventral sets are the most prominent muscles of the 
body wall. Between each two segments, from the fourth to the twelfth 
inclusive, a more or less spindle-shaped muscular band, called the znter- 
segmental muscle, touches both the dorsal and the ventral longitudinal 
muscles. There are two pairs of lateral longitudinal muscles on both 
sides which extend from the third segment to the twelfth. The more 
ventral muscle on each side comes anteriorly into contact with the cephalic 
retractor in the fourth and fifth segments but turns away before it 
terminates near the demi-annular muscles in the second segment, while 
