14 Journal New York Entomological Society, ["^'o'- ^^iv, 



which have both gills and paranotal structures, the paranota are 

 homodynamous with the wings, while the tracheal gills are not, this 

 would be a heavy blow to the tracheal gill theory, and a correspond- 

 ingly weighty argument in favor of the paranotal theory. Fortu- 

 nately, we have just such an insect, in the ''larva" of the singular 

 New Zealand Ephemerid Oniscigastcr zvakcficldi described by Mac- 

 Lachlan (1876). In the immature stages of this insect, the paranota 

 are borne along the sides of the tergal region (see Plate II, Fig. 15) 

 in the position characteristic of the wing location, while the tracheal 

 gills are borne high up on the dorsal region, and are not of the same 

 series as the wings. The abdominal paranota and the wings are both 

 retained in the adult condition, while the gills are lost when the insect 

 becomes mature, showing that they are merely temporary adaptational 

 structures, unlike the more lasting paranota. 



3. The paranota are borne along side of the tergal region in the 

 location characteristic of the wings, while the tracheal gills are at- 

 tached in a very different position, thus indicating that they are not 

 homologous with the wings. One has but to glance at Figs, i, 6 and 

 7 of Plate I, or at Figs. 8 and 12 of Plate II, to see that the wings 

 are always attached along the lateral margin of the principal tergal 

 plate, and the paranota (p of Figs. 9, 12, 14, 15, etc.) are attached to 

 the tergal region in exactly the same location; while the tracheal 

 gills are attached either to the posterior portion of the tergal region 

 (as in Fig. 4, Plate I) or to the dorsal region of the tergum (as in 

 Fig. 15 of Plate II), or occupy positions unlike that of the wings! 



4. The posterior margin of the principal tergal plate is always 

 continued in the posterior margin of the wing as the so-called spring 

 vein, ligament or axillary cord (Figs, i, 6, and 7 of Plate I). The 

 posterior margin of the tergum is contmued in the posterior margin 

 of the paranota (Figs. 9, 14, 15, etc., of Plate II) while the pos- 

 terior margin of the tergum is not continued in the tracheal gills 

 (Figs. 4 and 15). The inference is obvious! 



5. In Stciwdictya (Plate II, Fig. 8), Corydaloides (Fig. 12) and 

 other fossil insects, there occur lateral expanded structures on either 

 side of certain of the abdominal terga, which are homodynamous 

 with the wings and the prothoracic paranota. Certain palaeontolo- 

 gists have erroneously maintained that these abdominal structures 

 are gills, and since these structures are homodynamous with the 



