io8 THE INTEGUMENTAL SKELETON OF THE IMAGO. 



departure from his assumptions has found a place in recognised 

 text-books on morphology. 



Balfour [43, vol. i., p. 408], however, says ' the antennae can 

 hardly be considered to have the same morphological value as 

 the succeeding appendages ; they are, rather, equivalent to the 

 paired processes of the pre-oral lobes of the Chgetopoda.' And 

 Hatchett Jackson [44, p. 497] states that the head in insects 

 exhibits no trace of segmentation, except the appendages of 

 the three first post-oral metameres. 



Fir,. 21. — The Posterior surface of the Head Capsule of an immature Dragon-fly 

 {Libelhtia depressa) : e, epicranium ; J>c; paracephalon ; y, jugum ; md, mx', and 

 mx", the lateral piers of the mandibular and two maxillary segments ; c, galea 

 of maxilla ; Id, labium ; /l/' lateral lobe of labium (galea). The mandibles and 

 lacince of the maxilla are not represented. 



So far as I know, no one has as yet attempted to show the 

 limits of the somites which bear the mandibles and maxillae ; 

 even those who apparently recognise the non-segmental 

 character of the anterior part of the head capsule are silent 

 on the position and relations of the three post-oral cephalic 

 somites ; yet these segments are sufficiently distinct to be easily 

 recognised in the head capsule of immature specimens of Libel- 

 lula depressa and many other insects (Fig. 21). 



In order to attain a true conception of the nature of the 



