The morphology of Stigmaria has been much discussed; possibly the main axes, which do not agree perfectly either with rhizomes or roots, may best be regarded as comparable with the rhizophores of Selaginellae; they have also been compared with the embryonic stem, or protocorm, of certain species of Lycopodium; the homologies of the appendages with the roots of recent Lycopods appear manifest.
This can be proved to occur in a heart so embryonic that no nerves can be recognized in it, and in portions of cardiac muscle that contain neither nervecells nor nerve-fibres.
Successive observers in Italy, notably Fracastoro (1483-1553), Fabio Colonna (1567-1640 or 1650) and Nicolaus Steno (1638 - c. 1687), a Danish anatomist, professor in Padua, advanced the still embryonic science and set forth the principle of comparison of fossil with living forms. Near the end of the 17th century Martin Lister (1638-1712), examining the Mesozoic shell types of England, recognized the great similarity as well as the differences between these and modern species, and insisted on the need of close comparison of fossil and living shells, yet he clung to the old view that fossils were sports of nature.
The pro-deltidium, a term introduced by Hall and Clarke, signifies a small embryonic plate originating on the dorsal side of the body.
Of Macedon had begun his career of conquest, and had shattered an embryonic alliance between the league and certain princes of Thrace (Cetriporis), Paeonia (Lyppeius) and Illyria (Grabus).
Schwangart, who has studied (1904) the embryonic insects, twenty-one of these divisions - not, however, all similar - development of Lepidoptera.
Jacobson's organ has been lost by the birds, apparently without a trace in the embryonic fowl, but T.
Pascal also distinguished himself by his skill in the infinitesimal calculus, then in the embryonic form of Cavalieri's method of indivisibles.
The tegmen in most primitive forms, as well as in the embryonic stages of the living Antedon (fig.
The middle classes, which were making other countries rich and powerful, existed only in an embryonic condition.