I 



NO. 3 



INSECT HEAD SNODGRASS 



153 



migration from the tergal postoccipital ridge to the posterior ten- 

 torial apophyses. 



The question of the morphology of the cervical region of the insect 

 must yet remain a puzzle ; but the musculature gives no evidence of the 

 existence of a neck segment. On the other hand, the fold in the 

 integument of the caterpillar between the neck (fig. 57 D, Cv) and 

 the prothoracic tergum {To) is suggestive of being the true interseg- 

 mental line between the labial segment and the prothoracic segment, 

 and several muscles of the prothorax have their anterior attachments 

 upon it (D). If the primitive insect is conceived as a continuously 

 segmented, vermiform animal, the neck, or any other secondary inter- 

 segmental area, must be a part of a primary segmental region. From 

 the evidence at hand it seems more probable that the region of the 

 insect neck belongs to the labial segment, than to an anterior part 

 of the prothoracic segment. 



ABBREVIATIONS USED ON THE FIGURES 



Ab, abdomen. 



abplp, abductor of palpus. 



adplp, adductor of palpus. 



Am, amnion. 



AMR, anterior mesenteron rudiment. 



An, anus. 



Ant, antenna. 



AntNv, antennal nerve. 



Ao, aorta. 



AP, apical plate. 



AR, antennal ridge. 



Arc, archicerebrum. 



as, antennal suture. 



AT, anterior arm of tentorium. 



at, anterior tentorial pit. 



BC, body cavity. 

 Bdy, body. 

 Blc, blastocoele. 

 Bid, blastoderm. 

 Bp, blastopore. 

 iBr, protocerebrum. 

 2Br, deutocerebrum. 

 SBr, tritocerebrum. 

 Bs, basisternum. 

 BxiC, buccal cavity. 



CA, corpus allatum. 

 Cd, cardo. 

 Cer, cercus. 



Ch, chelicera. 



Cho, chorion. 



Clp, clypeus. 



CoeCon, circumoesophageal connective. 



Com, commissure. 



SConi, commissure of tritocerebral 



lobes. 

 Con, connective. 

 cs, coronal suture. 

 ct, coxo-trochanteral joint. 

 Cth, cephalothorax. 

 Cv, neck, cervix. 

 cv, cervical sclerite. 

 Cx, coxa. 



dap, dorsal apodemal plate of postoc- 

 cipital ridge. 



DMcl, dorsal longitudinal body muscle. 



DNv, dorsal longitudinal nerve. 



DT, dorsal arm of tentorium. 



dt, attachment of dorsal tentorial arm 

 to wall of cranium. 



E, compound eye. 

 Ecd, ectoderm. 

 End, endoderm. 

 Endp, endopodite. 



Ephy, epipharynx, epipharyngeal sur- 

 face. 

 Eps, episternum. 



