[25] Monog. of the Gymnoblastic or Tubularian Hydroids. See also Hincks, British Hydroid Zoophytes. Pl. x.
[26] Loc. cit. p. 315.
[27] Philosophical Transactions, 1859, p. 589.
[28] “Facts for Darwin,” Eng. Trans. p. 127.
[29] Rolleston, “Forms of Animal Life,” p. 146.
[30] A. Agassiz, “Embryology of the Starfish,” p. 25; “Embryology of Echinoderms.” Mem. of Am. Ac. of Arts and Sciences N.S. vol. ix. p. 9.
[31] Ueber die Gattungen der Seeigellarven. Siebente Abhandlung. Kön. Akad. d. Wiss. zu Berlin. Von Joh. Müller, 1855, Pl. iii. fig. 3.
[32] Huxley, Introduction to the Classification of Animals, p. 45.
[33] Philosophical Transactions, 1865 and 1866.
[34] Loc. cit. Zweit. Abh. Pl. i., figs. 8 and 9.