rOLSOM: MOUTH-PARTS OF ANUEIDA MAEITIMA. 127 



they are somewhat larger, and ventral or lateral surface views of the germ 

 band (Plate 2, Figures 9, 10 ; Plate 3, Figure 1 1) disclose a distinct lateral 

 lobe, the palpus (jjI]^.), which is larger than that of the first maxilla. 

 A second maxilla, as dissected out at this stage, is shown in Figure 18 

 (Plate 3). Transections of the germ band (Plate 3, Figure 14) show 

 the palpus to be an outfolding of the autero-lateral face of the primary 

 maxillary evaginatiou, just as in the case of the first maxilla. 



At this stage (Plate 2, Figures 9, 10) there appears near the mandibles 

 a lateral evaginatiou Q^li. or.) of the germ band, destined to form the 

 side of the face ; this fold grows backward until it involves the base of 

 the second maxilla of the same side, and the internal cavities of the two 

 folds become one. In Stage 4 (Figure 4; Plate 3, Figure 19) it has 

 already involved the base of the second maxilla ; the apex of the maxilla, 

 however, is still free from the fold, and the palpus (Plate 3, Figure 12, 

 pip.) is as large as that of the first maxilla. 



At Stage 5 the second maxillse (Figure 5 ; Plate 3, Figure 20, mxr) 

 are long, oval iu cross-section, and project at right angles to the germ 

 band ; the antero-lateral region of tlie base is confluent with the mouth- 

 fold (Figure 21). At this period all trace of the second maxillary palpus 

 becomes lost ; it has not become involved in the mouth-fold, which is 

 still restricted to the base of the maxilla, but has been rapidly resorbed 

 and appears at last as indicated in Figure 20. In the next stage (6) 

 the second maxilke (Figure 6) converge toward the median plane like 

 the other pairs of oral organs, and similarly swing forward. 



At Stage 7 (Plate 2, Figure 7) the second maxillse and mouth-folds 

 are quite confluent (Plate 5, Figures 30, 34), but the anterior part of 

 each maxilla is still distinguishable as a swollen lobe, or less flattened 

 region (Plate 4, Figure 24, lab.). The bases of the second maxillae, 

 although widely separated in Stage 5 (Plate 3, Figure 21, vix.'^), sub- 

 sequently spread toward the median plane, become thinner, and gradually 

 form a single plate ; the median sinus between them shortens until the 

 condition shown in Plate 5, Figure 29 (lab.) is attained. The union of 

 the second maxillie with each other is not a simple contact and fusion 

 resulting in a median suture ; but a confluence of the cavities of the two 

 maxillse occurs and progresses forward (i. e., distally), ceasing, however, 

 before oblitei-ating the median sinus, which remains iu the adidt (Plate 

 7, Figures 43, 45, sut. m. and sul.). Although the finished labium bears 

 a median ventral groove, the gi-oove does not indicate the fusion of the 

 fundaments ; at Stage 7, when the labial plate is complete, no trace 

 exists of the groove, which is formed in a later stage. A comparison of 



