THE FIGURE OF EIGHT. 

 FIG. i 



Fig. i, reproduced from J. Bell Pettigrew's "Animal Locomotion" 

 (Kegan Paul, Trench & Co., Ltd.), illustrate3 how the wing of a bird tends 

 to be twisted upon itself. It is that of a red-legged partridge seen from 

 behind and from beneath ; d and / are the anterior margin of the wing, 

 c and b are the posterior margin. 



FlG. 2 



Fig. 2, reproduced from M. Marey's "Animal Mechanism" (Kegan 

 Paul, Trench & Co. , Ltd. ), illustrates the 8 which is described by the whirring 

 wings of an insect hanging stationary in space. The extremity of each of 

 the larger wings of the insect a wasp was gilded, and a ray of the sun 

 cast upon it. 



