Xii LIST OF ILLUSTEATIONS. 



PAGE 



The Porpoise and Manatee, . . . . , 73 



The skeleton of the Diigong— (DaZ/as), . . .74 



The Seal, ....... 74 



The Sea-Bear, . . . . . . . 76 



The elliptical, looped, and spiral tracks made in swimming, . 81 

 The several attitudes assumed by the extremities in swimming 



in the prone position, . . . . .82 



Overhand swimming, . . . . . . 85 



Side swimming, . . . , . .80' 



Swimming of the Turtle and Triton, , , . .89 



Swimming of the Little Penguin, . . . . 91 



Sub- aquatic flight or diving, . . . . .94 



The feet of the Swan as seen in the open and closed condition, 96 

 The foot of the Grebe with swimming membrane — [Dallas], . 97 

 Double waved track described by the feet of swimming birds, . 97 

 The flight of the Flying-fish, . . . . . 98 



The wing a lever of the third order, . . . .105 



Figure-of-8 vertical track made* by the wing in flight, . . 107 



Do. horizontal track, . . . . .108 



Feathers and cork flying forward, . . . ,112 



Diagram illustrating how wings obtain their high speed, . 120 

 Butterfly with large wings, . . . . .124 



Beetle with small wings, . . . . .125 



Partridge witli small wings ; Heron with large wings, . 126 



The wings of the Hawk and Albatross, . . 136, 137 



The Green Plover with one wing flexed and the other extended, 138 

 Blur or impression produced on the eye by the rapidly oscillat- 

 ing wing of the insect, . . . . .139 



Diagram in which the down and up strokes of the wing of the 



insect are analysed, . . ' . . .141 



Diagrams illustrating the looped and waved tracks described 



by the wing of the insect, bat, and bird, . . .144 



Figures showing the positions assumed by the wing of the bird 



during the up and down strokes (side view), . . 145 



The positions assumed by the wing of the insect as it hastens 



to and fro and describes a figure-of-8 track, . . . 141 



The figure-of-8 curves made by the wing of the bird in flexion 



and extension, ...... 147 



The long and short axes of the wing, . . . . 149 



The waved tracks described by the wing and body of the bird 



as they alternately rise and fall, . . . 157, 103 



