182 



MR. R. J. TILLYARD ON THE RECTAL BREATHING-APPARATUS 



considerabl}^ longer than the other three, and the dorsal gill being the shortest 

 of all. The lengths of the gills are not constant, for, during the movements 

 of expansion and contraction of the rectum, not only their actual lengths, 

 but also their positions with respect to the abdominal segments, become 

 slightly altered. 



Each gill-fold is thrown into from six to nine very distinct undulations, 



:VT.. DT 



\ A. 



Text-fig. 18. — Anax papuensis, Burm. 

 Ventral view of gill-basket of newly hatched 

 larva. C'amera-lucida drawing. (X180.) 

 an, anal branch trachea ; c, cerci ; j\, first 

 junction ; j\, second junction ; Iv, 

 latero-ventral gill-fold ; hb, latero- 

 ventral branch of DT ; 7nv, mid-ventral 

 gill-fold ; VT, visceral tracheal trunk. 

 Other references as in text-fig. 17. 



Text-fig. 19. — Anax papuensis, Burm. 



Lateral view of gill-basket of newly hatched 



larva. Camera-lucida drawing, (x 180.) 



d, appendix dorsalis ; o, oblique trachea. 



Other references as in text-fip's. 17-18. 



