84 



PROCEEDINGS OF THE ACADEMY OF 



[March, 



rmc^t ^ 



Fig. 2. Diagram of the tracheation of the rectum of larva of Argia talaynanca, 

 reconstructed from sections. To avoid confusion the tracheae are represented 

 as lying farther to right and to left from the gut and from each other than is 

 actually the case (compare Fig. 1). Of the trachese which supply the gut walls, 

 those which run on the dorsal surface or enter the dorsal longitudinal fold are 

 shown in solid lines; those which run on the ventral surface or enter the lateral 

 folds are shown in broken lines. The ventral anastomosis is shown in dots and 

 dashes. The Roman numerals on the left side indicate the boundaries of the 

 respective abdominal segments; the larger Arabic numerals on the right, the 

 microscopic slides and the smaller Arabic numerals the rows of sections on each 

 slide of the series corresponding to that part of the diagram represented as at 

 the same horizontal level. Each row comprises about 30 sections. Abbrevia- 

 tions as in Figure 1 and as explained in the text. 



