BY R. J. TILLYARD. 11 1 



Again, taking the evidence of the wings themselves, the fore- 

 wings of our A nisoptera bear unmistakable evidences of 

 greater reduction than the hindwings, in the greater amount 

 of bending undergone by the triangle, which is evident in 

 the Corduliince, but far more evident in most of the Libellu- 

 lincn : and also in the distinctly compressed or slanting 

 arrangement of the cells along or near the posterior margin. 



The point I desire to emphasise is, that all the characters 

 of our present-day A nisoptera were developed out of existing 

 cell-material. Needham himself admits it in everything 

 except the anal loop, and he has treated the development of 

 the triangles in a very masterly manner. If his treatment 

 of ( 'onilcphya is correct, we must assume that a remarkable 

 caeuogenetic development of a whole host of anal cells in the 

 hmd-wing was begun, continued, and perfected during the 

 development of the Libellu/ida', bringing about the principal 

 differentiation between fore and hindwings. One has, how- 

 ever, only to look at the clear evidences of stretching, in a 

 direction across the wing-length, undergone by the anal cells 

 of any exceptionally broad-winged Lihelhdid, to see that the 

 anal loop and the broad hindwing basal area is only a 

 development of cells that xverc cdirays present there, right 

 back, through the aniso-zygopterid fossils, to the dawn of 

 the order. Further back than that, we have evidence that 

 many of the gigantic fossil insects of the Carboniferous age, 

 which are now generally agreed to be the ancestors of our 

 Odonata amongst other orders, possessed forewings that over- 

 lapped the hindwings. (See the figure of Titanophasma fayoli 

 Brogniart in Sharp's "Cambridge Natural History of In- 

 sects," p. 276.) 



I assume, therefore, contrary to Needham 's hypothesis, 

 that a moderately broad basal area of the hindwing was 

 originally present in the older Anisoptera, and that in this 

 area there were a large number of unarranged cells, from 

 which, by various degrees of rear7'angement and readjust- 

 ment, the different kinds of anal loops and supports now 



