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82 DESIGN IN NATURE<br />
PLATE LI<br />
Plate li. illustrates longitudinal, radiating, and transverse cleavage as seen in the tail of the manatee and<br />
dog-fish, in the wing and body of the insect, and in the wing of the bird and bat. These cleavages and radiating<br />
expansions are necessary for the purposes of locomotion in the water and the air.<br />
Fig. 1.—Various views of the swimming tail uf the manatee or sea-cow (Manahis americanus) as drawn by C. Berjeau, for Dr.<br />
James Murie, from a fresh specimen. The tail of the manatee is symmetrical, and more fleshy tlian that of the fish. In swimming it<br />
is made to vibrate vertically, as in the whale and other sea mammals, such as the rhytina, dugong, porpoise, &c. The vertical movements<br />
enable the air-breathing sea mammals readily to reach the surface, which is a necessity of their being. The arrangement<br />
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<br />
horizontally or laterally.<br />
A. The tail of young male as seen from the side and partly dissected, a, Skin ; b, vertebral column, showing transverse segmentation<br />
; c, right lobe of tail with skin in situ ; d, left lobe of tail with skin removed, showing radiating fibrous expansion of tail ;<br />
e, sacro-coccygeus and infra-coccygeus muscles, divided obliquely.<br />
B. Lateral view of tail. Shows symmetrical nature of the organ, the lower part of the body tapering to a point and terminating<br />
in the tail. The organ is fle.xible and elastic, as in the fish, and is a powerful propeller.<br />
C. Under surface of the tail. It lacks the conical ridge seen on the upper surface (B).<br />
Fig. -2.—Heterocercal or non-symmetrical tail of the large, male dog-fish as drawn by the Author from specimen in his possession.<br />
This form of tail has an eccentric movement which differs from that of symmetrical tails. Shows longitudinal and radiating cleavage<br />
in caudal fin and transverse cleavage in terminal portion of vertebral column ; this occupying the superior or major lobe. The tail is<br />
finely graduated in all directions and a powerful propeller, the dog-fish and shark families being the greyhounds of the ocean. The<br />
non-symmetrical and eccentric action of the tail increases the[degree of rotation in the body in swimming, and enables these voracious<br />
creatures, whose months are situated in the ventral surface, to turn readily on their side or back when seizing their prey. This affords<br />
a good example of design. ;f, Tapering terminal portion of spinal column ; a, h, c, superior margin of tail ; d,. e, inferior margin ;<br />
/, g, h, free margin.<br />
Pig. 3. —Right wing of male pheasant (Phasianus colchicus), seen from above. Drawn by C. Berjeau from a specimen in the<br />
Author's museum. Shows radiating cleavage to peifection. The wing, like all others, is triangular in sbape, and is flexible and<br />
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<br />
graduated structure, the mot being stronger than the tip and the anterior than the posterior margin. It forms the most complicated<br />
and perfect travelling organ known, and is a marvel of design. Each feather is a masterpiece in itself. The feathers are divided into<br />
three chief sets—the primary or rowing feathers, nine in number (d), the secondary feathers (e), and the tertiaries (/). The main covering<br />
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<br />
literally to tread the air, this affording very little support when contrasted with the water and the earth. It has, moreover, to support<br />
as well iis propel. Viewed from every point it is one of nature's triumphs.<br />
Pig. 4.—Body and right wing of hat (Vespertilio viurinus), seen from above. Drawn by C. Berjeau from a specimen in the Author's<br />
museum. The bat is tlie oiilj' mammal which flies. Its wings present extraordinary modifications of the anterior extremities. They<br />
are outstanding examples of adaptation of means to ends, and afford a unique example of design. Shows division and radiation in the<br />
anterior and posterior extremities, body, and tail, which support the flying membrane. This, as in the insect (Fig. 5 of this Plate), is<br />
not broken up, but continuous. In the bird (Pig. 3 of this Plate) the flying membrane is composed of feathers which can be separated.<br />
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<br />
semi-rigid margin of wing ; 6, posterior, thin, higlily elastic margin.<br />
Pig. 5.—Body, right wing, and wing case of large beetle (Goliafhus inicans), seen from above. Drawn by C. Berjeau from specimen<br />
in the Author's museum. Shows radiating and transverse division in the wing and body. The wing greatly resembles that of the<br />
bat in genera] structure, consisting as it does of a continuous membrane supported by a radiating framework of elastic materials (vanes).<br />
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<br />
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<br />
when not in use, and protected by the wing cover or elytron (c).<br />
Fig. 6.—Right wing of the albatross (Dioniedea exulans\ seen from above. Drawn by the Author from a specimen in his possession<br />
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<br />
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<br />
wing. The priinary or rowing feathers, nine in number, are seen at d; the secondary feathers at c; and the tertiary feathers at /.<br />
While all wings are triangular in shape and carefully graduated, they are shorter or longer according to requirement Compare the<br />
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<br />
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.<br />
PLATE LII<br />
Plate hi. illustrates the manner in which the travelling organs, originally formed by budding and by longitudinal,<br />
radiating, and transverse cleavages, are modified in animals widely divergent, to meet the requirements of transit<br />
in water and air. All the swimming animals which hve in the water conform, as a rule, to the fish shape ; the<br />
swimming organs, whether fins, flippers, wings or feet, being similarly constructed, and acting on a common principle.<br />
Pig. 1.—The sea-bear (Otaria hookeri). Drawn by 0. Berjeau from life. Shows greatly modified anterior and posterior extremi<br />
ties; the former being converted into flippers which greatly resemble wings, the latter being expanded like fish tails The animal<br />
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<br />
swim after the manner of the fish. The Author has frequently witnessed both kinds of progression. The specially i. ^ modified l,'n,k'= , I<br />
plainly the outcome of design.<br />
^ nmob are<br />
Pkj. 2.—The seal (Phoca fmtida). Drawn Ijy C. Berjeau from life. The extremities are smaller and still more modified th-n<br />
the sea-bear. The general shape of the body, moreover, is more fish-like, In both the sea-bear and seal the anterior extremitie"^