How ironic. In order to avoid the "nutty" theory of inversion, Gaskell invented the even odder notion of stomachs turning into brains with new guts forming below. No wonder then, that later biologists cast a plague on both speculative houses and opted instead for the obvious alternative: arthropods and vertebrates do not share the same anatomical plan at all, but rather represent two separate evolutionary developments of similar complexity from a much simpler common ancestor that grew neither a discrete gut nor a central nerve cord.
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"Brotherhood by Inversion", p. 327Stephen Jay Gould
» Stephen Jay Gould - all quotes »
Geoffrey also recognized that the opposite orientations of gut and nervous system posed a problem for his claim that insects and vertebrates represent different versions of the same archetypal animal - and he proposed the first account of the inversion theory to resolve this threat to unification. ...Geoffroy pursued the... aim of establishing a "unity of type" that could generate both arthropods and vertebrates from the same basic blueprint. ...The single grand design includes a gut in the middle and the main nerve cords somewhere on the periphery.
Stephen Jay Gould
Gaskell... had to keep his stately soldiers upright and uniformly oriented... by crafting the brain and spinal cord from an arthropod digestive tube, while forming a completely new gut below. ...Gaskell thought that his move would rescue the theory of linear progress, with its necessary transition of arthropod into vertebrate, from the absurdities of the old inversion theory.
Stephen Jay Gould
Arthropods and vertebrates share some broad features of general organization - elongated, bilaterally symmetrical bodies, with sensory organs up front, excretory structures in the back, and some form of segmentation along the major axis. But the geometry of major internal organs could hardly be more different... Arthropods concentrate their nervous system on their ventral (belly) side as two major cords running along the bottom surface of the animal. The mouth also opens on the ventral side, with the esophagus passing between the two nerve cords, and the stomach and remainder of the digestive tube running along the body above the nerve cords. In vertebrates, and with maximal contrast, the central nervous system runs along the dorsal (top) surface as a single tube culminating in a bulbous brain at the front end. The entire digestive system then runs along the body axis below the nerve cord.
Stephen Jay Gould
Later evolutionary theorists of linear progress had to advance the overtly physical and historical claim that an ancestral lineage of arthropods actually turned over to become the first vertebrates (for the classical statement of the inversion theory, see William Patten, The Grand Strategy of Evolution, 1920).
Stephen Jay Gould
"Most biologists," (says Vogel, 1981) "seem to have heard of the boundary layer, but they have a fuzzy notion that it is a discrete region, rather than the discrete notion that it is a fuzzy region."
Bill Mollison
Gould, Stephen Jay
Govorov, Leonid
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