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Several cases are on record of the same species presenting varieties in the upper and lower parts of the same formation. Thus Trautschold gives a number of instances with Ammonites, and Hilgendorf has described a most curious case of ten graduated forms of Planorbis multiformis in the successive beds of a fresh-water formation in Switzerland.
Heterocerus, stridulation of. Hewitt, Mr., on a game-cock killing a kite; on the recognition of dogs and cats by ducks; on the pairing of a wild duck with a pintail drake; on the courtship of fowls; on the coupling of pheasants with common hens. Hilgendorf, sounds produced by crustaceans. Hindoo, his horror of breaking his caste.
And it was not, as Hilgendorf thought, in a series which can be traced in the strata according to time, but, as Sandberger says, in quite a varied mixture, yet in all imaginable modifications. But even among the higher and the highest classes of animals, we can trace the transitions.
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