136 bulletin: museum of compakatiye zoology. 



the mandibles in rate of downward growth, and the lateral surface of 

 the mandible to be concave, in conformity with the swollen distal region 

 of the mouth-fold. 



In Stages 6 and 7 (Plate 1, Figure 6 ; Plate 2, Figure 7) the folds in- 

 volve the labrum and second maxillse (Plate 4, Figure 24 ; Plate 5, Figure 

 30, pli. or.), covering the mandibles and first maxillse laterally, and form- 

 ing the genee, or sides of the face. As seen in Stage 7 (Plate 5, Figure 

 30), each oral fold connects one side of the clypeo-labral fold with the 

 labial evagination of the same side. There are no sutures, however, to 

 indicate the union of the gente dorsally with the clypeus and ventrally 

 with the second maxilla, for the oral evagination, in its backward and 

 forward extension, has at length involved the labial and clypeal folds, 

 respectively, in such a way that all three folds become one and enclose 

 a single common cavity. The anterior margin of the mouth-fold is still 

 distinguishable, however, as late as Stages 7 and 8 (Plate 4, Figure 24, 

 pit. 07'.) ; the mesal surfaces of the labial fundaments have not luiited 

 anteriorly (Plate 5, Figui*e 29) ; the labrum is free from the fold (Figure 

 30) and remains so. The mouth is definitely bounded, but still open 

 (Figui'es 30, 34) ; its closure occm-s, however, before the egg hatches. 

 The folds — clypeo-labral, oral, and labial — have been converging con- 

 comitantly with their elongation, and continue to elongate and converge 

 until they meet to form a buccal cone, which completely encloses the 

 inner mouth-parts. After hatching, there is, for reasons just given, no 

 demarcation of the mouth-fold ; it can simply be said that the region 

 designated as pli. or. in Figure 40 (Plate 6) is the anterior part of that 

 fold. Also in Orchesella the corresponding region, under which project 

 the palpi (Folsom, '99, Plate 2, Figure 9), doubtless originates as in 

 Anurida, but the clypeus is not confluent with the folds. 



Strictly speaking, then, the mandibles and maxillae are not '* retracted," 

 as is usually stated ; but they are overgrown by the genoe. 



Hansen ('93, p. 208) wrote concerning Campodea, Japyx, and Collem- 

 bola, " die Mandibeln und Maxillen, mit Ausnahme der Spitzen, ' im 

 Kopfe liegen.' Dieses ist dadurch entstanden, dass sich die Haut hintir 

 ihrer Einlenkung wie eine Duplicatur, welche Gewebe enthalt, vorwilrts 

 und um sie herura gefaltet hat, und die Rander dieser Duplicatur sind 

 auf der Unterseite des Kopfes mit dem Seitenrflndern des Labiums 

 festgewachsen, so dass dieses fast seiner ganzen Lange nach mit der 

 Seitenwand des Kopfes verbunden ist." These facts he ascertained by 

 laborious dissections of the finished parts. 



Packard ('71, p. 21) simply mentions that " the cephalic plates, which 



