82 DESIGN IN NATURE 



PLATE LI 



Plate li. illustrates longitudinal, radiating, and transverse cleavage as seen in the tail of the manatee and 

 dog-fish, in the wing and body of the insect, and in the wing of the bird and bat. These cleavages and radiating 

 expansions are necessary for the purposes of locomotion in the water and the air. 



Fig. 1. — Various views of the swimming tail uf the manatee or sea-cow (Manahis americanus) as drawn by C. Berjeau, for Dr. 

 James Murie, from a fresh specimen. The tail of the manatee is symmetrical, and more fleshy tlian that of the fish. In swimming it 

 is made to vibrate vertically, as in the whale and other sea mammals, such as the rhytina, dugong, porpoise, &c. The vertical move- 

 ments enable the air-breathing sea mammals readily to reach the surface, which is a necessity of their being. The arrangement 

 is not accidental, and affords a proof of design. The movement differs from that of the tail of the fi.sh, which is made to vibrate 

 horizontally or laterally. 



A. The tail of young male as seen from the side and partly dissected, a, Skin ; b, vertebral column, showing transverse segmen- 

 tation ; c, right lobe of tail with skin in situ ; d, left lobe of tail with skin removed, showing radiating fibrous expansion of tail ; 

 e, sacro-coccygeus and infra-coccygeus muscles, divided obliquely. 



B. Lateral view of tail. Shows symmetrical nature of the organ, the lower part of the body tapering to a point and terminating 

 in the tail. The organ is fle.xible and elastic, as in the fish, and is a powerful propeller. 



C. Under surface of the tail. It lacks the conical ridge seen on the upper surface (B). 



Fig. -2. — Heterocercal or non-symmetrical tail of the large, male dog-fish as drawn by the Author from specimen in his possession. 

 This form of tail has an eccentric movement which differs from that of symmetrical tails. Shows longitudinal and radiating cleavage 

 in caudal fin and transverse cleavage in terminal portion of vertebral column ; this occupying the superior or major lobe. The tail is 

 finely graduated in all directions and a powerful propeller, the dog-fish and shark families being the greyhounds of the ocean. The 

 non-symmetrical and eccentric action of the tail increases the[degree of rotation in the body in swimming, and enables these voracious 

 creatures, whose months are situated in the ventral surface, to turn readily on their side or back when seizing their prey. This affords 

 a good example of design. ;f, Tapering terminal portion of spinal column ; a, h, c, superior margin of tail ; d,. e, inferior margin ; 

 /, g, h, free margin. 



Pig. 3. — Right wing of male pheasant (Phasianus colchicus), seen from above. Drawn by C. Berjeau from a specimen in the 

 Author's museum. Shows radiating cleavage to peifection. The wing, like all others, is triangular in sbape, and is flexible and 

 elastic. It tapers from the root towards the tip and from the anterior (a, b, c) towards the posterior (d, e, f) margin. It is a carefully 

 graduated structure, the mot being stronger than the tip and the anterior than the posterior margin. It forms the most complicated 

 and perfect travelling organ known, and is a marvel of design. Each feather is a masterpiece in itself. The feathers are divided into 

 three chief sets — the primary or rowing feathers, nine in number (d), the secondary feathers (e), and the tertiaries (/). The main covering 

 feathers of the wing are seen between a, b, g. The wing of all the travelling organs is the largest as compared with the body. It has 

 literally to tread the air, this affording very little support when contrasted with the water and the earth. It has, moreover, to support 

 as well iis propel. Viewed from every point it is one of nature's triumphs. 



Pig. 4. — Body and right wing of hat (Vespertilio viurinus), seen from above. Drawn by C. Berjeau from a specimen in the Author's 

 museum. The bat is tlie oiilj' mammal which flies. Its wings present extraordinary modifications of the anterior extremities. They 

 are outstanding examples of adaptation of means to ends, and afford a unique example of design. Shows division and radiation in the 

 anterior and posterior extremities, body, and tail, which support the flying membrane. This, as in the insect (Fig. 5 of this Plate), is 

 not broken up, but continuous. In the bird (Pig. 3 of this Plate) the flying membrane is composed of feathers which can be separated. 

 The wing of the bat, as in the bird, is flexible, elastic, and finely graduated. It forms a perfect organ of flight, a, Anterior, thick 

 semi-rigid margin of wing ; 6, posterior, thin, higlily elastic margin. 



Pig. 5. — Body, right wing, and wing case of large beetle (Goliafhus inicans), seen from above. Drawn by C. Berjeau from specimen 

 in the Author's museum. Shows radiating and transverse division in the wing and body. The wing greatly resembles that of the 

 bat in genera] structure, consisting as it does of a continuous membrane supported by a radiating framework of elastic materials (vanes). 

 The wing is beautifully graduated, being thicker at the root and along the anterior margin, where it is jointed (a), tlian at the tip and 

 along the posterior margin (b). It is flexible and elastic in all its parts, as in other wings. It can be folded on the back of the insect 

 when not in use, and protected by the wing cover or elytron (c). 



Fig. 6. — Right wing of the albatross (Dioniedea exulans\ seen from above. Drawn by the Author from a specimen in his possession 

 This forms the longest and narrowest of all wings. The wing here represented is 6 feet long by 9 inches wide. It resembles that of 

 other birds if allowance be made for its greater length and narrowness, a, b, c, Anterior margin of wing ; d, e,f, posterior margin of 

 wing. The priinary or rowing feathers, nine in number, are seen at d; the secondary feathers at c; and the tertiary feathers at /. 

 While all wings are triangular in shape and carefully graduated, they are shorter or longer according to requirement Compare the 

 wmg of the pheasant (Fig. 3 of this Plate) and that of the albatross (Fig. 6 of this Plate), and both with that of the bat (Fig 4 of this 

 Plate) and that of the insect (Fig. 5 of this Plate). The long wings are adapted for slow movements, the short ones for quick movements. 



PLATE LII 



Plate hi. illustrates the manner in which the travelling organs, originally formed by budding and by longitudinal, 

 radiating, and transverse cleavages, are modified in animals widely divergent, to meet the requirements of transit 

 in water and air. All the swimming animals which hve in the water conform, as a rule, to the fish shape ; the 

 swimming organs, whether fins, flippers, wings or feet, being similarly constructed, and acting on a common principle. 



Pig. 1.— The sea-bear (Otaria hookeri). Drawn by 0. Berjeau from life. Shows greatly modified anterior and posterior extremi 

 ties; the former being converted into flippers which greatly resemble wings, the latter being expanded like fish tails The animal 

 can fly through the water at a great speed with its flippers, or it can employ its expanded, webbed hind extremities as fish tiils an,l 

 swim after the manner of the fish. The Author has frequently witnessed both kinds of progression. The specially modified l,'n,k'= , I 

 plainly the outcome of design. i. ^ ^ nmob are 



Pkj. 2.— The seal (Phoca fmtida). Drawn Ijy C. Berjeau from life. The extremities are smaller and still more modified th-n ■ 

 the sea-bear. The general shape of the body, moreover, is more fish-like, In both the sea-bear and seal the anterior extremitie"^ 



