88 DESIGN IN NATURE 



PLATE LIV 



that the lower limbs plait and o^'erlap slightly in walking : they in fact form complemental and opposite curves in each successive 

 step, as shown at Plate liii.. Figs. 2 and 4. A similar plaiting of the limbs occurs in the walking of the bird (Figs. 7 and 10 of this 

 Plate), and in the walking and running of quadrupeds, as for example the horse, &c. (Fig. 1 of this Plate). 



Fig. 4. — Double, complemental, figure-of-8 spirals made by the wing of the bird in extension and flexion, as drawn by the Author 

 in 1867. The solid line and arrows indicate the double curve made by the wing in extension ; the interrupted line and arrows the 

 double curve made by the wing in flexion. 



Fig. 5. — Shows the iigure-of-B movements made by the wing of the wasp in active flight, and also the angles made by the wing 

 with the horizon at every part of each stroke, as figured by the Author in 1867 and 1870. In tiie insect the direction of the .stroke is 

 more horizontal than in the bird and bat. The forward and backward stroke and figure-of-8 made by the tip of the left wing is seen 

 in the two upper figures at a, h, c, d, e, f, cj, and at g, h, i, j, k, I. The various angles made by the left wing with the horizon at successive 

 stages of the forward and backward stroke and when reversing are given in the two lower figures. The same letters in the upper and 

 lower figures represent the wing in the several phases through which it passes during the forward and backward stroke. 



Fig. 6. — The cicada (C. septemdecim). Shows four typical wings. As the wings are transparent the venation and structure can be 

 seen to great advantage. The two right and the two left wings, when taken together, present a triangular outline; the roots of the 

 wings being thick and semi-rigid, the tips thin and elastic. The anterior margins, moreover, are thicker than the posterior ones. The 

 wings taper in two directions, namely, from the lOots to the tips, and from the anterior to the posterior margins. They are carefully 

 graduated structures and, as such, perfect organs for aerial locomotion. Wings so constructed inevitably fly forward during both the 

 down and up strokes when made to vibrate. Drawn by C. Berjeau from specimen in the Author's museum. 



Fig. 7. — Photograph of the ostrich (Struthio camelus), as seen from behind, rnnning. Shows how the right leg {a) and left wing 

 and shoulder (6) move together to form a double diagonal curve (see darts) and one step ; and how the left leg (c) and right wing 

 and shoulder (d) move together to form a second and opposite double diagonal curve (see dart) and a second step. These move- 

 ments are repeated so long as the bird continues to run (the Author). 



Fig. 8. — Diagram constructed by the Author in 1867 to show that the wing of the bird, contiary to prevailing belief and pre- 

 conceived notions, strikes downwards and /orjoarcfe during tlie down stroke. Prior to 1867 tlie wing was supposed to strike verticallj' 

 downwards or downwards and hachioards. The Author's view has been confirmed by instantaneous photography, and is now generally 

 accepted, x, Axis of body of bird ; d, root of wing ; a, a', double forward curve made by tip and posterior margin of wing during their 

 descent ;/,/', similar but opposite curve made by root and anterior margin of wing. The two margins make double and opposite 

 diagonal curves when the wing is in action. The wing, as a matter of fact, twists and untwists diagonally during the down and up 

 strol;es, and makes figure-of-8 movements similar to those made by the tails of fishes, the flippers of sea mammals, and the extremities 

 of quadrupeds and bipeds. 



Fig. 9. — Photograph of vulture ( Vultur monachus), flying with the wings flexed as seen during the up stroke, and fully extended as 

 seen during the down stroke and in sailing flight. During the up stroke the wings are not only flexed or folded, but all the feathers 

 are separated so as to diminish to the utmost the resistance experienced from the superimposed air. During the down stroke the wino- 

 is fully opened out and extended, and the feathers, for the most part, tightly closed to seize and prevent the escape of the nether aiit 

 The right wing of the lower figure is twisted upon itself, and forms double figure-of-8 curves (the Author). 



Fig. 10. — Photograph of the adjutant (Giconin alba) walking. This quaint bird walks precisely as a man does : thus it begins its 

 step by extending the toes of the right foot (1st figure, left side) ; it then folds and shortens the right leg (2nd figure) ; it then advances 

 the right leg and folds the right foot (3rd figure) ; it then straightens the right foot and somewhat straightens and advances the right 

 leg (4th figure) ; it then further straightens and advances the right leg and straightens and points the right foot downwards 

 (5th figure) ; it then still further straightens and advances the right leg and spreads out the toes of the right foot preparatory to 

 placing the right foot on the ground (6th figure). This completes one step. During the step the right leg and foot make a curve the 

 convexity of which is directed outwards or towards the spectator (see darts). The left leg and foot perform precisely similar move- 

 ments in making a second step, and make an opposite or complemental curve (the Author). 



§ 10. Recapitulation. 



The points which I have endeavoured to establish by the aid of the foregoing illustrations are : 



1. That many crystals bear a strildng resemblance to plants and animals and parts thereof. 



2. That crystals in many cases present radiating, branching, segmented, and concentric arrangements also found 

 in plants and animals. 



3. That crystals form frost pictures and dendrites which resemble plants and animals and also electric sparks 

 and lightning flashes. 



4. That crystals in some cases form spirals which resemble the fronds, tendrils, and other parts of plants, 

 and the bones, horns, teeth, and other parts of animals. 



5. That plants and animals are composed, for the most part, of the same elements and have much in common ■ 

 their constituent parts being, in the majority of cases, arranged in radiating, branching, and concentric lines, with 

 longitudinal and transverse cleavages in a more or less marked form. 



6. That these cleavages also occur in inorganic matter, as in basaltic rock formations. 



7. That the basaltic columns form pentagonal, hexagonal, and other prisms, which find their counterparts in 

 certain corals; these again resembhng the prisms found in the enamel of teeth, the fasciculi of muscles, and as 

 far as general outhne is concerned, the cells of the honeycomb, epidermic cells, pigment cells, &c. 



8. That organic structures which are widely separated and which apparently have nothing in common do ne 



