THE EMBRYOLOGY OF THE HONEY BEE 177 



45 Ten). From the ends of this bar spring two pairs of arms, 

 one pair anterior (iTen) and the other posterior (zTefn). 

 These arms join the chitinous cuticle of the head. The tentorium 

 thus serves as a set of braces to support and strengthen the 

 cranial capsule as well as to serve for the attachment of muscles. 

 The posterior arms (zTen) together with the central body 

 (Ten) form a flat arch, its convex side directed cephalad. The 

 outer ends of these arms are attached to the cranial capsule low 

 down on its lateral aspect, near its junction with the trunk. The 

 anterior arms, which are much more slender than the posterior, 

 arise also from the ends of the central body and are here about 

 equidistant both from one another and from the lateral wall of 

 the head. Each takes a course dorsad, and only slightly laterad, 

 to a point on the anterior cranial wall just above the base of each 

 mandible. About midway between the central body and the anter- 

 ior cranial wall the anterior arms give off a short pointed spur, 

 directed laterad and cephalad (Fig. 69B). In all of the more 

 advanced larvae studied the anterior arms are much longer than 

 the posterior, but in recently hatched larvae (Fig. XV) the arms 

 are nearly equal in length. As is evident in figure XV the anter- 

 ior arms together with the central body form a U-shaped struc- 

 ture which embraces the oesophagus and the circumoesophageal 

 commissure. 



The tentorium serves for the attachment of two pairs of large 

 muscles, besides a group of small muscles near the mid-line. 

 Both pairs of large muscles are inserted on the wall of the head. 

 The first of these is attached to the tentorium at the ends of the 

 central body, and from' here each member of the pair runs ven- 

 trad, ectad and caudad, to an attachment of the hypodermis at 

 the base of the first maxilla. The muscles of the second pair are 

 attached to the anterior arms of the tentorium, just cephalad of 

 their junction with the central body, and run obliquely dorsad, 

 laterad and cephalad to a broad area of attachment on the cranial 

 wall, laterad of the cephalic lobes. It is presumably the tendon 

 of this muscle which forms the spur on the anterior arms (Fig. 

 69B). Muscle fibres also pass from the anterior margin of the 

 central body to the posterior (ventral) wall of the pharynx and 

 doubtless serve as dilators of the latter. 



