similar view that the stomach-diverticula of the
Turbellaria, which he had found to be segmentally arranged in certain
Triclads, were the morphological equivalents of the enterocoelic pouches
of higher animals. This view, however, he soon gave up.[454] Sedgwick's
views found a supporter in A. A. W. Hubrecht,[455] who utilised them in
connection both with his speculations on the relation of Nemertines to
Vertebrates, and with his exhaustive work on the early development of
the Mammalia. He postulated as the far-back ancestor of Vertebrates, "an
actinia-like, vermiform being, elongated in the direction of the
mouth-slit" (p. 410, 1906), and derived the central nervous system from
the circum-oral ring of this primitive form, the notochord from its
stomodaeum, and the coelom from the peripheral parts of the gastric
cavity (p. 169, 1909).

[424] Gegenbaur, _Zeits. f. wiss. Zool._, v., 1853.

[425] Remak, _loc. cit._, p. 183, pl. xii.

[426] Lereboullet, _Ann. Sci. nat._ (4) xviii., pp. 118-9,
1862.

[527] Lereboullet, in Remak, p. 183 f.n.

[428] Kowalevsky, _Mem. Acad. Sci. St
Petersbourg_ (Petrograd), (7), x. and xi., 1866 and 1867.

[429] A. Agassiz, _Contrib. Nat. Hist. United States_, v.,
1864.

[430] _Mem. Acad. Sci. St Petersbourg_ (Petrograd), (7),
xiv., 1869.

[431] "Embryolog. Studien an Wuermern u. Arthropoden,"
_Mem. Acad. Sci. St Petersbourg_ (Petrograd), (7), xvi.,
1870.

[432] _Die Kalkschwaemme_, 3 vols., Berlin, 1872. General
chapters translated in _Ann. Mag. Nat. Hist._ (4), xi.,
pp. 241-62, 421-30, 1873.

[433] "Die Gastraea-Theorie, die phylogenetische
Classification des Thierreichs und die Homologie der
Keimblaetter." _Jenaische Zeitschrift_, viii., pp. 1-55,
1874. "Die Gastrula und die Eifurchung der Thiere,"
_ibid._, ix., pp. 402-508, 1875. "Die Physemarien,
Gastraeaden der Gegenwart," and "Nachtraege zur
Gastraea-Theorie," _ibid._, x., pp. 55-98, 1876.
Republished in _Biologische Studien_, 2nd part, _Studien
zur Gastraea-Theorie_, 270 pp., 14 pls., Jena, 1877.

[434] See _Ann. Mag. Nat. Hist._ (4), xi., p. 253.

[435] Term first introduced in _Die Kalkschwaemme_, p. 468,
1872.

[436] "On the Primitive Cell-layers of the Embryo as the
Basis of Genealogical Classification of Animals, and on
the Origin of Vascular and Lymph Systems," _Ann. Mag.
Nat. Hist