OF MAXILLUL/E in the orders of insects. 



437 



that of a similar pair which have been described in CMoeon, if we regard the 

 structures (m.) as the homologies of the maxillulfe of this Ephemerid. 

 Further comparison gives additional grounds for this assumption. The 

 lateral lobes are in both cases fused with the hypopharynx on its dorsal 

 surface. They extend beyond it laterally. In both cases they are supported 

 ventrally by a chitinous plate, and a transverse bar of chitin (text-figs. G 

 & 7) marks the Hue of junction to the upper surface of the hypopharynx. 



The difference existing between Nemura and CMoeon in respect of these 

 organs appears therefore to be concerned merely with the degree of fusion 

 of their adjacent surfaces. 



Text-fia-. 5. 



Nemura sp. Tongue, dnrso-lateral aspect, x 250. /(. Hypopharynx. m. Maxillula. 

 p. Transverse sclerite at base of maxillula. p.m. Plate in ventral wall of maxillula. 



PSOCIDiE axd MALLOPHAGA. 



The tongue of Psocidse (text-fig. 6) and Mallophaga bears a pair of oval, 

 or sole-shaped, structures (p.) as to the nature of which considerable con- 

 troversy exists. They were described by Burgess (5) in the Psocidre and 

 termed "lingual glands," but Burgess suggests that this term mioht not 

 correctly express their nature. The chitinous cord (ex.) proceedino- from 

 each, which unite, and pass backwards as a single cord, to be attached to the 

 "bonnet-shaped" skeletal structure (o.s.), are referred to as "ducts" of these 

 glands. Among later writers this interpretation has been followed by 

 Snodgrass (43) and Shipley (41). The "glands" are, however, considered 

 to. be chitinous thickenings of the hypopharynx by Grosse (19), Mjoberg (34), 



