1920] Dii Porte: Muscular System of Gryllus 23 



The Retractor of the Hypopharynx (Fig. 6, r.hyp.) is a long 

 flat muscle having its head contiguous to that of the retractor 

 of the labium. It runs parallel to this muscle and is inserted 

 into the side of the hypopharynx near the junction between this 

 organ and the labium. 



The Epipharynx. There is a single median epipharyngeal 

 muscle (Fig. 9, eph.m.) which has the form of a truncated cone. 

 Its points of attachment are the inner sides of -the labium and 

 epipharynx. 



(b). Muscles of the Antennce. 



There are three muscles within the head which bring about 

 the movements of the antenna as a whole. (Fig. 5, m.ant.) 



The Extensor of the Antenna (Fig. 11, ext.ant.) originates 

 from the dorsal side of the lateral angle of the anterior tentorial 

 plate and is inserted into the lateral side of the base of the first 

 antennal joint. 



The Flexor of the Antenna (Fig. 11, fl.ant.) This muscle 

 has its origin near the apical angle of the central tentorial plate 

 in the angle formed by the anterior and posterior plates. It is 

 inserted at the inner side of the basal margin of the first antennal 

 segment. 



The Depressor of the Antenna (Fig. 11, dep.ant.) has a very 

 broad head attached to the dorsal side of the anterior arm 

 of the tentorium and extending from the epicranium to the 

 attachment of the anterior plate to the central plate. It tapers 

 rapidly and is inserted into the ventral side of the basal segment 

 of the antenna. 



Within each antennal segment there is a flexor (Fig. 10, 

 fl.a.s.) and an extensor (ext.a.s.) similar to those described in 

 the palpi. 



(c). Muscles of the Pharynx and Oesophagus. 



The circular or constrictor muscles are well developed in the 

 oesophagus. In addition to these there are several muscles 

 originating in the wall of the head or the tentorium which 

 function as dilators and suspensors of the pharynx and 

 oesophagus. 



The Precerebral Dorsal Dilators (Figs. 5 and 6, pr.d.) There 

 are usually three paired dilator muscles lying in front of the 

 brain. The first (pr.d.i) has its origin in the clypeus and is 



