70 ORGANIZATION AND DEVELOPMENT OF ANIMALS IN GENERAL. 



walls, traversed by numerous septa and folds which bear an extremely 



rich network of capillaries. The air tubes or trachece (fig. 65) consti- 

 tute a branched system of canals 

 which extend throughout the 

 whole body, and carry the air 

 to all the organs. Thus instead 

 of the respi- 

 ratory pro- 

 cess being 

 localised, as 

 it is in ani- 

 mals with 

 lungs, it is 

 carried on in 

 all tissues 

 and organs 

 of the body, 

 which are 

 surrounded 

 by a fine ^ 



trachea! network. Nevertheless, the air tubes 



in the case of the modification known as fan- 



trachece present an approximation in their 



structures to lungs, in that the main stems, 



without further branching, give rise to flat 



hollow leaves. 



i iia 



Fio. 65. Tracheae with fine brauches 

 (after Leydig). Z, cellular outer wall ; 

 Sp, spiral thread. 



Via. CGi. Lateral view of head and body of nn 

 Acridium. St, stigmata ; T, Tympanum. 



Openings in the body wall are present, placing 

 the organs of aerial respiration in communica- 

 tion with the exterior. These openings may 

 be numerous, and paired, placed symmetrically on the sides 



FIG. GCa. Tracleal sye 

 tem of a Diptei.-:is 

 larva. 2V, Longitudi- 

 nal stem of the right 

 side with tufts of tra- 

 cheae; St', and St", 

 anterior ami posterior 

 stigmata ; J/A, oral 

 hooks. 



