DEVELOPMENT 



121 



At the anterior end of the germ band is a pair of large procephalic 

 lobes (Figs. 193, 195), which eventually bear the lateral eyes, and im- 

 mediately behind these are the funda- 

 ments of the antennae. The funda- 

 ments of the primary paired append- 

 ages are out-pocketings of the ecto- 

 dermal germ band, and at first an- 

 tennae, mouth parts and legs are all 

 alike, except in their relative positions. 

 Behind the antennae (in Thysanura 

 and Collembola at least) appears a 

 pair of rudimentary appendages (Fig. 

 195, /) which are thought to represent 



the second antennae of Crustacea; instead of developing, they disappear in 

 the embryo or else persist in the adult as mere rudiments. In front of 

 these transitory intercalary appendages is the mouth-opening, above which 



s ' . < g 



FIG. 194. Diagrammatic sagittal 

 section of hymenopterous egg to show 

 stomadaeal (5) and proctodaeal (/>) in- 

 vaginations of the germ band (g). After 

 GRABER. 



~~pr 



FIG. 195. Ventral aspect of germ 

 band of a collembolan, A unrida maril- 

 ima. a, antenna; a 1 - a 5 , abdominal ap- 

 pendages; /, intercalary appendage; 

 /, labrum; //, left labial appendage; 

 m, mandible; mx, maxilla; p, pro- 

 cephalic lobe; pr, proctodseum; t l -t 3 , 

 thoracic legs. 



si I 



V. 



g 



FIG. 196. Anterior aspect of embryonal mouth 

 parts of a collembolan, A unrida niaritima. a, an- 

 tenna; /, labrum; /g, prothoracic leg; li, left funda- 

 ment of labium; /, lingua; m, mandible; ;K.V, max- 

 illa; p, maxillary palpus; si, superlingua. After 

 FOLSOM. 



the labrum and clypeus are already indicated by a single, median evagina- 

 tion. Behind the mouth the mandibles, maxillae and labium are repre- 



