THE GILL-CHAMBER OF DRAGONFLY NYMPHS 



347 



branching in Lanthus is markedly different from that in any- 

 other form studied. 



9. There is a three-lobate valve at the caudal end of the 

 rectum. 



10. The Zygoptera show no gill chamber, but have an enlarged 

 ampulla just caudad of the Malpighian tubules. In Calopteryx 

 the rectum is enlarged to form a second ampulla, but it does not 

 resemble the anisopteran rectum. 



11. The following table will show the number of respiratory 

 parts found in each rectum. The figures are approximate, 

 except for the longitudinal folds; they are based on average 

 numbers of gills from several rows and average numbers of villi 

 from many gills. 



BUTTRESS 

 FOLDS 



LONGITUD- 

 FIN.U, 

 OLDS 



Cordulegaster. . . 



Aeschna 



Basiaeschna 



Boyeria 



An ax (A. Junius) 



Lanthus 



Hagenius 



Ophiogomphus. . 



Gomphus 



Didymops 



Epicordulia 



Dorocordulia 



Tetragoneuria. . . 



Helocordulia 



Leucorhinia 



Sympetrum 



Pachydiplax. . . . 



Libellula 



Plathemis 



Tramea 



Pantala 



216 

 280 

 280 

 280 



180 



216 



1601 

 (240)1 

 (160)1 

 360 

 360 

 360 

 350 

 370 

 216 

 200 

 360 

 340 

 340 

 360 

 360 



1950 



1900 

 4800 

 2900 



1 Morphologically present, not functional in respiration. 



