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The Descent of Man

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mestication why I now place little reliance on<br />

the recorded cases <strong>of</strong> such regrowth. Nevertheless<br />

it deserves notice, inasmuch as arrested<br />

development and reversion are intimately related<br />

processes; that various structures in an<br />

embryonic or arrested condition, such as a cleft<br />

palate, bifid uterus, etc., are frequently accompanied<br />

by polydactylism. This has been<br />

strongly insisted on by Meckel and Isidore<br />

Ge<strong>of</strong>froy St.-Hilaire. But at present it is the safest<br />

course to give up altogether the idea that<br />

there is any relation between the development<br />

<strong>of</strong> supernumerary digits and reversion to some<br />

lowly organised progenitor <strong>of</strong> man.) <strong>The</strong>re are<br />

other cases which come more strictly under our<br />

present head <strong>of</strong> reversion. Certain structures,<br />

regularly occurring in the lower members <strong>of</strong><br />

the group to which man belongs, occasionally<br />

make their appearance in him, though not<br />

found in the normal human embryo; or, if normally<br />

present in the human embryo, they become<br />

abnormally developed, although in a

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