ENTOGNATHY IN APTERYGOTES — TUXEN 



583 



I have stressed this point in order to avoid separating more than 

 necessary the three entognathous groups from each other. 



2. WHAT IS ENTOGNATHY? 



This problem may be approached through embryological and mor- 

 phological investigations. 



The embryology of Campodea "staphylimis Westw." (Diplura) 

 was studied by Uzel (1898; see his figs. 38 and 39 and especially figs. 



0.0 1 mm 



Fig. I. — Accrentomon doderoi Silv. Pseudoculus with nerve and muscles seen 

 from inside the cranium ; the same pseudoculus from different angle. 



77-83), that of Protjapyx maior Grassi by Silvestri (1933), who also 

 gave a description of the mouth parts in what he calls the prelarva 

 and the "larva primae aetatis" (see also Silvestri, 1948, pp. 284-286). 

 The postlarval development of Campodea, especially C. rhopalota 

 Denis, was studied by Orelli (1956), who, however, does not give 

 figures of the mouth parts, but I have been allowed to see some of 

 his slides, for which I am very grateful. 



Uzel describes how just before the invagination of the embryo into 

 the yolk (the blastokinesis) a fold appears lateral to the mouth parts, 

 extending from the second maxillae to the intercalary segment. This 

 fold, which later was given the name plica oralis, in its growth will 

 enclose the mandibles and first maxillae in a cavity ventrally closed 



