IN THE LA.RV^ OF ANISOPTERID DRAGONFLIES. 



181 



turn and travels round it completely, until the whole series of folds with 

 their contained loops is clearly outlined by the air within. Regular move- 

 ments of contraction and expansion of the rectum take place from this time 

 onward. 



(2) A description of the gill-hasket audits tracheal supply 

 during the second instar. 



We have seen that the original air-supply of the gill-basket is not derived 

 from water drawn into the rectum, but comes from some source in the 

 anterior portion of the larva, and enters the gills through the main tracheal 

 trunks. Let us now study the formation of the gill-basket as it is to be seen 

 in the transparent larva shortly after the first ecdysis. 



■DT 



Text-fig. 17. — Anax papuensis, Burm. 

 Dorsal view of gill-basket of newly-hatched larva. Camera-lucida drawing. (xl80.) 

 DT, dorsal tracheal trunk ; dv, dorsal vessel or heart ; J2, second junction ; Id, latero-dorsal 

 gill-fold ; md, mid-dorsal gill-fold ; plb, postero-lateral branch of DT ; pmb, postero- 

 median branch of same. 6-10, abdominal segments. 



The six longitudinal gill-folds lie in the rectum in positions corresponding 

 to the numbers 2, 4, 6, 8, 10, 12 on the clock-face. They are not all of the 

 same length, the ventral gill-fold and the two latero-dorsals {i. e. the three 

 gills corresponding to the numbers 2, 6, 10 on the clock-face) being 



LINN. JOURN. ZOOLOGY, VOL. XXXIII. 13 



