NO. 3 INSECT HEAD SNODGRASS 89 



is the true base of the palpus {iplp) — therefore, not the palpifer. 

 which lacks muscles — and that the lobe in question is not the galea, 

 as also the absence of a muscle to it would indicate. The maxilla of 

 the Sialis larva, then, is not a generalized appendage in the sense that 

 Crampton would infer, since it lacks a true galea and is provided with 

 an accessory lobe on the first segment of the palpus. Similar lobes 

 of the palpus segments occur in other insects, particularly in larvae 

 of Coleoptera ; they have a suggestion of the endite lobes of the telo- 

 podite in such crustaceans as Apus (fig. 35 C). 



In the thoracic legs the limb is always flexible at the union between 

 the basis and the telopodite, i. e., at the coxo-trochanteral joint, and 

 in no appendage, where the facts can be clearly demonstrated, is 

 there a union between the coxa and the trochanter. It does not seem 

 reasonable, therefore, to suppose that the proximal segment of the 

 telopodite (the trochanter) should have been incorporated into the 

 limb base in the case of a maxillary appendage. Especially is such 

 a supposition unreasonable in the face of nnich specific evidence to 

 the contrary. The whole body of evidence l)earing on the limb mech- 

 anism points to a primitive uniformity of flexure in all the appen- 

 dages, whereby the limb is divided into a basis and a telopodite. and 

 indicates that the articulation between these two parts is preserved in 

 the entire series of appendages, except, of course, where the telo- 

 podite is lost. 



The maxillipeds and the anterior body appendages of Apus bear 

 each five endite lobes. The first lobe (fig. 35 C, Be) is a basendite, 

 the second is carried by the proximal division of the trochanter, the 

 third by the femur, the fourth by the tibia, and the fifth by the tarsus. 

 Each endite is independently movable by muscles inserted upon or 

 within its base. The maxillae of Apus are reduced to single lobes, but 

 the first maxilla appears to represent the rudimentary limb base with 

 the large basendite, since it falls exactly in line with the series of 

 basal endites on the following appendages. The basal endites of 

 arthropod limbs in general, including the " gnathobases " of the trilo- 

 liite appendages, the gnathal lol)es of the pedipalps in Xiphosura and 

 Arachnida, and the " styli " of the legs of Scolopendrella, are almost 

 certainly analogous lobes in all cases, and they must be represented 

 by the laciniae (at least) of the insect maxillae, by the laciniae of the 

 mandibles of diplopods and chilopods, and by the incisor and molar 

 lobes of the mandibles in all arthropods. It is a question, therefore, 

 whether the galea of the insect maxilla is an accessory lobe of the 

 limb base, or a subdivision of the primary basendite (fig. 35 B, C, Be) 

 The latter seems probable, since, in the more generalized insects, the 



