Neither male nor female has wings; the rostrum is replaced by a functionless tubercle; and there is no alimentary canal.
He has observed that in young specimens of Siren lacertina (the larva is still unknown) the gills are rudimentary and functionless, and that it is only in large adult specimens that they are fully developed in structure and function; he therefore concludes that the sirens are the descendants of a terrestrial type of batrachians, which passed through a metamorphosis like the other members of their class, but that more recently they have adopted a permanently aquatic life, and have resumed their branchiae by reversion.
They hay e large heads, projecting incisors, no ears, almost functionless eyes and moderately long tails; the skin, with the exception of a few hairs on the body and frinr-es on the feet, being naked.
394), being apparently led to that conclusion through its functionless wings and the backward situation of its legs.
The resemblance of the spermatia and spermogonia to those of Uredineae should be pointed out, where also there is considerable evidence for their original sexual nature, though they appear in that group to be functionless in all cases.
The singular fact requires to be noticed that in both these species the hind toe is generally deficient, but that examples of each are occasionally found in which this functionless member has not wholly disappeared.
Between the long, extensile, worm-like tongue of the anteaters, essential to the peculiar mode of feeding of those animals, and the short, immovable and almost functionless tongue of the porpoise, every intermediate condition is found.
It remains to be seen if the ovuliferous cone in the centre of the flower represents simply a functionless gynoecium, as in Welwitschia and abnormal cones of certain Coniferae, or if the flowers were hermaphrodite, with both male and female organs fully developed.