ENTOGNATHY IN APTERYGOTES — TUXEN 



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of these drawings to be able to give a series of cross sections of the 

 head showing the shape of the atrium and the gnathal pouches, but 

 this proved to be unsatisfactory without true microscopical sections. 

 Nassonow (1887) has, however, given very convincing cross sections 

 of the head of Campodea "staphylinus" anterior to the antennae 

 (figs. 25 and 38), at the middle of the head (fig. 28) and at its hind 



0.05 mm 



Fig. 5. — Campodea plusiochaeta Silv. Head with maxillae and fulcrum, 

 dorsal, mandibles omitted. Maxillae dotted. 



part (fig. 29), as well as before and behind the "appendages" of the 

 labium (figs. 40 and 39). Snodgrass (1951, fig. 30 D) gives a cross 

 section of the head of Heterojapyx gallardi Till. 



The main points are the following : The mandibles and the maxillae 

 are hollow at the inner and upper sides, especially distinct for the 

 mandibles. The cavity contains the muscles as shown in a later chap- 

 ter. At the original sternal part of the head is found a system of rods, 



