6 Proceedings of the Royal Irish Academy. 



moved respectively by the muscles H, L, N, and T. Two nerves pass 

 up the centre of the palp, and in places are apt to be mistaken for delicate 

 muscles. A muscle {B) from the base of the stipes moves the galea, and 

 perhaps bends back both galea and lacinia as a whole. Anteriorly a stronger 

 muscle {A), arising also from the base of the stipes, is inserted by a broad 

 tendon into the internal basal corner of the lacinia ; it is joined by a, slender 

 muscle {Q) from the epicranium. These muscles bend the lacinia, and with it 

 the galea, forwards. 



The strange suggestion of Verhoeff ('05), that the labium is really anterior 

 to the maxillae, finds no support in the musculature of those parts, as the 

 muscles of the maxillae that come from the tentorium all originate anteriorly 

 to those passing from there to the labium. 



The theoretical interpretations of the jointing of the maxilla are numerous. 

 All appear to regard the car do as the basal segment, though, as has been 

 pointed out above, it might perhaps be composed of two segments. Marshall 

 and Hurst ('99) regard the stipes and cardo as homologous with the protopodite 

 of the Crustacea, the palp as an exopodite, the galea and lacinia as a divided 

 endopodite. Henneguy ('04) regards the stipes as a second segment, which is 

 followed by a third bearing as an internal ridge, the lacinia, the galea forming 

 a fourth and terminal segment; segments three and four constituting the 

 endopodite, the palp the exopodite. Lang ('91) and Boas ('96) regard the 

 galea and lacinia as mere masticatory ridges of the stipes segment, and I am 

 not acquainted with their views with respect to the succeeding palp segments. 

 Chatin, in his comparative account of the jaws of biting insects ('84), adopts a 

 somewhat empirical threefold division of the maxilla into basal, central, and 

 appendicular portions. Hansen ('93), who appears to have very carefully gone 

 into the matter, regards the lacinia as the masticatory lobe of the second or 

 stipes segment, while the third segment, which is cut off from this very 

 obliquely, bears the palp and galea. On mere examination of forms like 

 Periplaneta, one would, perhaps, accept this view with extreme hesitation ; 

 but in a specimen of Praemachilis wdiich I examined, the galea certainly 

 appeared to be but an internal appendage of a thu-d segment which carried 

 the palp. Hansen, who holds that insect appendages are directly comparable 

 with those of Malacostraca, regards the palp as endopodite. His extended 

 observations do not apparently give any support to the theory that the galea 

 is homologous with the crustacean endopodite; indeed, the only fact that 

 favours that theory seems to be the segmentation of the galea in certain forms 

 less generalized than the Orthoptera — i.e., in the Adephaga, or carnivorous 

 Coleoptera. Moreover, Verhoeff ('04) points out that the galea and lacinia are 

 very possibly homologues of the coxal organs present upon the basal segment 



