24 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



rod has evidently been pulled back, as far as its ligament (Fig. 18 lig.) 

 allowed, by the action of the adductors of the head, and must manifestly 

 be thrust forward before it can again be withdrawn. This protrusion of 

 the rod appears to be a necessary result of the simple protrusion of the 

 stipes, by muscles Nos. 9, 5, and G ; the advancing stipes pushes forward 

 both the head and the attached chitinous rod until the ligament of the 

 latter has become tense in the opposite direction. 



The above explanation of the movements of the terminal portion of 

 the maxilla is the only one I can offer, after long study. It appears 

 reasonable to me, and accounts for the presence of the peculiar chitinized 

 tendon or rod of the maxilla, as well as the unique ligamentous connec- 

 tion between the maxilla and paraglossa. I shall again refer to this 

 connection when describing the palpi. 



The maxillae are supplied by the second pair of nerves from the infra- 

 cesophageal ganglion ; each nerve begins at the side of the ganglion, a 

 little behind the mandibular nerve, goes directly outwards for a short 

 distance and enters the maxilla at the posterior end of the chitinous ex- 

 pansion ; a branch is soon given off to the palpus. The anterior portion 

 of the maxilla is occupied by a core (Fig. 1 9, gl. et n.) of filamentous cells 

 which penetrate into the lobes of the laciuia through an orifice in the 

 base of the head of the maxilla; these filamentous cells are of two kinds 

 and precisely similar to those already described for the labrum, the base 

 of certain cells containing a large oval nucleus (Fig. 19), while inter- 

 vening cells are ganglionic, with small round nuclei. The maxilla is 

 lined with a single layer of confluent hypodermis cells, deeply pigmented 

 and containing round nuclei of moderate size. 



Palpi. 



The palpi, consisting of but one pair, are of special interest because von 

 Stummer-Trauufels considered them quite anomalous in position, having 

 described and figured them as separated from the maxilhe and joined to 

 the paraglossse. This author ('91, p. 226) emphasizes, "Die grosse 

 Unwahrscheinlichkeit, dass der sogenannte Maxillartaster der Collem- 

 bolen wirklich zur Maxille gehort, indem diese von jeuem vollstandig 

 getrennt ist und derselbe vielmehr in innigem Verbande mit der Para- 

 glossen steht." This view originated, however, with Tullberg, as his 

 description and figure show. I believe that this view is erroneous, and 

 that the palpi unquestionably belong to the maxilla?; I shall show how 

 the mistake mentioned might easily be made. 



Each palpus (Fig. 18, pip.) is finger-shaped and composed of but a 



