152 Prof. J. Wood-Mason's Morpliological Notes 



portions of the terminal free joint, tlie endopodite and 

 exopodite respectively of the embryonic crustacean man- 

 dible. If the view here suggested be correct, the possi- 

 bility of the occurrence of a mandibular palp in insects 

 and myriopods is altogether excluded, the extremities of 

 both the branches of the ])rimitive member entering into 

 the formation of the functional jaw ; and the peculiar 

 appendages found on the inner side of the mandibles in 

 many Coleoptera acquire a definite morphological signifi- 

 cation, I refer to the 'prostheca' of Kirby and Spence, 

 and to the structures homologous with it in beetles other 

 than Staphylinid(B. In the ' Devil's Coach-horses' ( Goerius 

 olens), in IStaphylinus erythroj^terus, and other ' Rove- 

 beetles,' and in the sub-aquatic Heteroceridce, no molar 

 process is developed; but in its place, movably articu- 

 lated to the jaw, is a membranous ciliated appendage not 

 unlike the endopodites of Scolopendrella. I am con- 

 vinced that this is an endopodite, and. that it answers to 

 the molar branch of the jaws in Blatta and Machilis. It 

 has its homologue in the diminutive Trichopteryyiidce in 

 the firmly-chitinized quadrant-shaped second mandibular 

 joint, which is used in a peculiar manner * in crushing the 

 food. It is rej)resented by the membranous inner lobe of 

 the mandibles in the Goliath beetles of Southern Asia, 

 which inner lobe frequently becomes indurated and grooved 

 internally so as to function as a feeble crusher of the soft 

 food of these insects, in many Phytophaga, and in Donacia, 

 which is considered by some to bridge the interval between 

 these last and the longicorns ; in some of which, as, for 

 instance, in Batocera, a wrinkled papilliform scar remains 

 to mark its former presence. f 



4§. One of the most interesting and remarkable features 

 in the whole organization of the Thysanura is the presence 

 of abdominal appendages, which, in Machilis, are movably 

 articulated to the hinder margin of the sterna of the eight 

 antepenultimate somites, a pair to each somite. Sir John 

 Lubbock was, I believe, the first to put upon record the 

 important fact " that each of the four posterior legs bears 

 au appendage on the basal segment closely resembling the 



* Mathews, 'Monograph of Trichopterygiidte.' 



I It is probably represented also by the movably-articulatcd and firmly- 

 chitinized appendage, shaped like the terminal joint of one of the palpi, 

 which I have discovered on one of the mandibles in Australian, Asiatic, 

 African and South American PassnUdcc. But in this case the large 

 molar surface of the mandible must be a process of the cutting portion. 



