128 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



my figures (Plate 3, Figure 20; Plate 5, Figure 29) will show that 

 practically the entire veutral surface of the head is labial in origin, be- 

 cause the original bases of the second maxillae extended quite to the first 

 pair of legs ; an inconsiderable, if any^ portion of the germ band inter- 

 vening (Figure 21) between them. 



At Stage 8 the mouth is nearly closed (Plate 5, Figure 34) by the 

 overgrowth of the combined second maxillae and mouth-folds. 



In the adult (Plate 7, Figure -43) the apical lobes, although in con- 

 tact mesally and stoutly chitiuized, are readily separable and may be 

 depressed and elevated by muscles homologous with those of Orchesella, 

 the hinge lines being shown at siit. Shortly befoi'e hatching, hypbdermis 

 cells evaginate singly to form the external setJB of the head. 



In the development of the labium, as I have tx-aced it, neither galea 

 nor lacinia becomes differentiated ; but the terminal lobe is equivalent 

 to the head of the first maxilla, and therefore represents the common 

 fundament of galea and lacinia, the second maxilla not passing the 

 biramous stage. All of the labium behind the terminal lobe represents 

 not only the stipes and cardo of the first maxilla, but also the mentum, 

 submentum, and gula of the Orthopteran labium, — an important 

 conclusion. 



In Orchesella (Folsom, '99, Plate 3, Figure 24) mentum, submentum, 

 and gula appear to be indicated, but the development in Auurida throws 

 no light upon the structures which I suggested might be modified palpi. 



Pacliard ('71, p. 17) in describing Isotoma says, "I was unable at 

 this or any other period to discover any traces of the second maxillae. 

 Though existing in a very rudimentary state in the adult, I could not 

 detect them after repeated attempts, but do not doubt but that a more 

 skilled observer would have made them out. Indeed, it is a most diffi- 

 cult thing to discover their rudiments in the adult ; I failed, at the time 

 these observations were made, to detect them, though since then I have 

 succeeded in making out their structure and relation to the sun-ounding 

 parts of the mouth." As a matter of fact, he (Plate 3, Figure 13) has 

 evidently figured the second maxilhie, which I know to be present in the 

 genus, and in the passage quoted he doubtless referred to the super- 

 linguae ("paraglossae"), which Lubbock also ('73, p. 66) termed "second 

 maxilhe." Kyder ('86, Plate XV. Figures 7, 9, 10), too, repeated the 

 mistake in Anurida. 



Claypole ('98, Plate XXIII. .Figures 40-44, 46, 47) represents tlio 

 fundaments as simple papillne without distinguisliing the palpi, which 

 are, however, obscurely indicated in Figures 43 and 47. 



