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Updated: May 5, 2025
They explain also in the most interesting manner how certain characters have originated, such as the indented ocelli on the tail-feathers of the peacock, and the ball-and-socket ocelli on the wing-feathers of the Argus pheasant.
As the secondary plumes became lengthened through sexual selection, and as the elliptic ornaments increased in diameter, their colours apparently became less bright; and then the ornamentation of the plumes had to be gained by an improvement in the pattern and shading; and this process was carried on until the wonderful ball-and-socket ocelli were finally developed.
Perfect Joints. There are various forms of perfect joints, according to the nature and amount of movement permitted. They an divided into hinge joints, ball-and-socket joints and pivot joints. The hinge joints allow forward and backward movements like a hinge. These joints are the most numerous in the body, as the elbow, the ankle, and the knee joints.
Nevertheless I know of no fact in natural history more wonderful than that the female Argus pheasant should appreciate the exquisite shading of the ball-and-socket ornaments and the elegant patterns on the wing-feather of the male.
These latter ornaments have been shewn to many persons, and all have admitted that they are beautiful, some thinking them even more so than the ball-and-socket ocelli.
Foot: 7 Tarsal or ankle bones, 5 Metatarsal or instep bones, 14 Phalanges, or toes bones, making 30 bones in all. The Thigh. The longest and strongest of all the bones is the femur, or thigh bone. Its upper end has a rounded head which fits into the acetabulum, or the deep cup-like cavity of the hip bone, forming a perfect ball-and-socket joint.
Their connection with the shell is very remarkable, for it is by a ball-and-socket joint, the same articulation which gives the human hip its marvellous liberty of action. Between them are five rows of minute holes, and, in life, a transparent, hair-like foot is protruded from each, at the pleasure of the owner.
If the bone is rarefied, the enlarged cancellous spaces are opened into and an eroded and worm-eaten appearance is brought about; with further use of the joint, the bone is worn away, so that in a ball-and-socket joint like the hip, the head of the femur and the acetabulum are markedly altered in size and shape.
The upper part of the ring consists of two or three separate portions; and there is only a trace of the thickening of the portion which forms the black mark above the white shade. This white shade itself is not as yet much concentrated; and beneath it the surface is brighter coloured than in a perfect ball-and-socket ocellus.
Externally, the firing mechanism consisted of a pistol grip and trigger, which looked all right to me. The sight was a standard binocular light-gun sight, with a spongeplastic mask to save the gunner from a pair of black eyes every time he fired it. The elevating and traversing gear was combined in one lever on a ball-and-socket joint.
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