Mouth-parts in a Species of Polyplax 



259 



(see fig. 2). A curious ''duct" (or chitinous chord), cross- 

 barred like a trachea, runs forward from between tlie anterior 

 cornua of tiie sclerite and bifurcates in front, each branch 

 running into a basal piece or '' gland/' which is, according to 

 Armenaute, only a itard flat oval piece of chitin, Avithout 

 glandular structure. 



Fio:. 2. 



Diagrammatic sketch of the oesophageal sclerite (or lyriform organ) and 

 " glands " (or basal pieces) in Mallophaga. 



G = Gland: S = Sclerite. 



The infra-buccal plate in P. hrachyrhynchus is apparently 

 fused at least in part with the lower wall of the head. It is 

 extremely minute and correspondingly difficult to dissect, as 

 the whole head itself in this species measures only "20 of a 

 millimetre in length. The vestigial character of this plate 

 and the two chitinous chords, which arise from between 

 the two anterior horns by separate roots, is indicated by the 

 delicacy and, in different specimens, by the varying outline 

 of the parts. Both plate and chords are present in all 

 specimens, however, and the former stains deeply with acid 

 fuchsin. On one side in the specimen from which the 

 drawing is made indications of a " gland " or basal piece 

 were observed, and its outline is therefore given. 



An infra-buccal plate is present in other species o( Poli/plaw, 

 including P. spinulosa. 



