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MISS A. M. EVANS ON THE STRUCTURE AND OCCURRENCE 



The structure o£ the hypopharynx and maxillulse is illustrated in text-fig. 1. 

 The hypopharynx measures - 09 mm. in length and "12 mm. in greatest 

 breadth. In its natural condition it is almost obscured by the maxillulas (m.), 

 which are articulated at (a.) to a short branch of the skeletal support (*.). 

 They are laminar, and can be removed entirely from the hypopharynx. The 

 distal portion is triangular and the pointed apex furnished with sharp teeth 

 directed inwards. The dorsal surface is covered with seta:, those of the 

 anterior and inner areas being borne by scales arranged in rows. Each 

 maxillula measures "11 mm. in length and - 05 in total width. 



Lepismidce. — Hansen (21) states that in the structure of the hypopharynx 

 Lepisma stands between Machilis and the Orthoptera. His statement is 

 referred to by Carpenter (8. p. 13), who described the tongue of Isolepisma 

 and the maxillula: borne by it. These latter have "a roughened apex, with 



Text-fig. 2. 



Lepisma sacckarma. Dorsal aspect of tongue. /;. Hypopharynx. m. Its maxillulav surface. 

 p.e. Peduncles, r. Longitudinal ridge marking inner edge of maxillula. /. Anterior 

 transverse bar of skeletal system. 



fine short bristles," and there is " no differentation into lacinia and galea." 

 The tongue of Lepisma sacchanna (text-fig. 2) is a broad membranous 

 structure closely applied to the surface of the labium. It is supported distally 

 by a system of sclerites, composed of elements corresponding to those of 

 Isolepisma. The width at the base is "2 mm. and the distance from the 

 transverse bar (t.) to the anterior edge '12 mm. The maxillula: have become 

 completely fused with the tongue, of the upper surface of which they form 

 the lateral portions, being separated from the median scaly portion by 

 longitudinal ridges (?'.). 



CoUembola. — Maxillula: appear to be present in all Collembola as a pair of 

 delicate lamella: intimately associated with the hypopharynx. A frequently 



