Thus instead 



-Mh 



70 OHGANIZATION 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 tracheae (fig. 65) consti- 

 tute a branched system of canals 

 which extend throughout the 

 whole body, and carry the air 

 to all the organs, 

 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- 



tracheoi present an approximation in their 



structures to lungs, in that the main stems, 



without further 



hollow leaves. 



FIG. 65. Traehese with fine branches 

 (after Leydig). Z, cellular, outer wall ; 

 Sp, spiral thread. 



Tr- 



branching, 



give 



rise to flat 



T 



'St 



FIG. 666. Lateral view of head and body of an 

 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. 6G. Tracteal .^y* 

 tern of a Dipterous 

 hu-vsi. Tr, Longitudi- 

 nal stem of the right 

 side with tufts of trn- 

 chese; St', and St", 

 anterior and posterior 

 stigmata; Mh, or;il 

 hooks. 



