Ammocffitus(-es) Larval form of *lampreys, resembling *lancelets in shape and behaviour, and used once by CD to illustrate forms that lack *complexity.
Amphibians A class of vertebrates which includes the frogs, toads and newts (i.e. the 'batrachi-ans'), sporting a mix of features which renders them in some ways 'intermediate' between primitive fishes and early reptiles (though one must be wary of such linear *scale).
CD suggested once that the *lungfish Lep-idosiren mediates between fish and amphibians: Unknown form probably intermediate between mammals, Reptiles & Birds as intermediate as Lepidosiren now is between Fish and Batrachians (Corresp. to C. *Lyell, Sept. 23, 1860). He did this only once, presumably because the lungfishes, at the time, were perceived to be amphibians.
The larval form of amphibians, the tadpole, provides a model for the early chordates. The similarities between larval *seasquirts and tadpoles are particularly striking, and are commented upon by CD. (See also Vertebrate origins; Lancelet; Ontogeny.)
Amphidromy(-ous) A questionable form of *diadromy, referring to fishes that migrate between freshwater and the sea, but not for the purpose of breeding, as *anadromous and *catadromous species do.
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