620 



ZOOLOGY 



SECT 



trachese. In the Spiders there are either four pulmonary sacs 

 (Fig. 515), or two pulmonary sacs and a system of trachese (Fig. 516). 



3: 



Tracheae are present in the Phalangida and also in the majority 

 of the Acarida. In the Xiphosura the organs of respiration are 



