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There are two types of classification, homology and analogy. Homology is the fundamental identity of structure, as distinguished from analogy, which incidental resemblance in form or function. Bird wing showing homolog and analogy

Bird Wing

There are two types of classification, homology and analogy. Homology is the fundamental identity of…

An illustration of an "elastic spiral wing, which twists and untwists during its action, to for a mobile helix or screw. This wing is made to vibrate by a direct piston action, and b a slight adjustment can be propelled vertically, horizontally or at any degree of obliquity." -Britannica, 1910

Elastic Spiral Wing

An illustration of an "elastic spiral wing, which twists and untwists during its action, to for a mobile…

"Ammodramus. Seaside Sparrow. Bill remarkably slender and lengthened for this family, with culmen toward end, gonys straight, and sometimes an evident lobation of the cutting edge of the upper mandible. Wings short and rounded, yet longer than tail; inner secondaries, though not elongate, reaching nearly to end of primaries when wing is closed; point formed by 2d-4th quills. Feet large and stout, reaching outstretched about to the end of tail; tarsus about equal to middle toe and claw in length; lateral toes of equal lengths, very short, their claws under reaching base of middle claw. Tail shorter or not longer than wings, much rounded, of narrow, stiffish, sharp-pointed feathers. Embracing small streaky marsh sparrows, especially of the sea-coast, but not exclusively maritime, as long supposed; remarkable for slenderness of the bill, sharp narrow tail-feathers, and stout feet fitted for grasping slender swaying reeds. Edge of wing bright yellow; a yellow spot of buff stripe on head; upper parts olive-gray or quite blackish, streaky." Elliot Coues, 1884

The Details of a Seaside Sparrow

"Ammodramus. Seaside Sparrow. Bill remarkably slender and lengthened for this family, with culmen toward…