^{page 55 note 1} See, for example, Robson, G. C., “A Note on Species as a Gene-complex”: Ann. Mag. Nat. Hist., (9) xi, 1923, p. 111.CrossRefGoogle Scholar

^{page 55 note 2} This was suggested by Déperet in 1909 (Transformations of the Animal World, p. 191). A distinguished palaeontologist, in a letter to the writer, suggests that the difficulty arises from the attempt to put palaeontological wine into neontological bottles! It may be suggested that, in general, a “species” in palaeontology is more comprehensive than a species in neontology.

^{page 56 note 1} Lamplugh, G. W., “On the Junction of Gault and Lower Greensand”: Q.J.G.S., lxxviii, 1922, p. 1, note.CrossRefGoogle Scholar

^{page 57 note 1} Carruthers, R. G., “The Evolution of Zaphrentis delanouei”: Q.J.G.S., lxvi, 1910, p. 523.CrossRefGoogle Scholar

^{page 57 note 2} Hickling, G., “The Variation of Planorbis multiformis”: Manchester Memoirs, lvii, 1913, p. 1.Google Scholar

^{page 57 note 3} Trueman, A. E., “The Use of Gryphaea in the Correlation of the Lower Lias”: Geol. Mag., LIX, 1922, p. 256.CrossRefGoogle Scholar

^{page 57 note 4} Alkins, W. E., “Morphogenesis of Brachiopoda”: Manchester Memoirs, lxvii, 1923, p. 1.Google Scholar

^{page 57 note 5} Klahn, Hans, “Der Wert der Variationsstatistik für die Paläontologie”: Berichte d. Nat. Gesellsch. z. Freiburg, 1920, p. 1.Google Scholar

^{page 57 note 6} It must, of course, be remembered, as Mr. S. S. Buckman has repeatedly urged, that the finding of specimens in one block of stone is not necessarily proof of contemporaneity, but in the above instance the variation curves show that at each horizon the group is homogeneous; this would be unlikely if the group included derived specimens of various dates.

^{page 57 note 7} Hickling, , op. cit., pp. 4, 19.Google Scholar

^{page 58 note 1} This method of expressing the problem is adopted from H. H. Swinnerton, Outlines of Palaeontology, 1923, p. 391.Google Scholar

^{page 58 note 2} Nevertheless, the “species” of the palaeontologist is generally much broader than that of the neontologist.

^{page 58 note 3} Swinnerton, H. H., “The Use of Graphs in Palaeontology”: Geol. Mag., LVIII, 1921, pp. 406–8.Google Scholar

^{page 58 note 4} A somewhat similar conception is suggested by Lang, W. D., Proc. Geol. Assoc., xxxiv, 1923, p. 132.Google Scholar

^{page 59 note 1} Vaughan, A., “The Palaeontological Sequence in the Bristol Area”: Q.J.G.S., lxi, 1905, p. 183.Google Scholar

^{page 59 note 2} Compare, W. D. Lang, Catalogue of Cretaceous Bryozoa (British Museum), iii, 1921, p. ii.Google Scholar

^{page 59 note 3} Useful summaries of some of these conclusions will be found in the following: Robson, G. C., op. jam. cit.;Google Scholar Davis, B. M., “Species, Pure and Impure”: Science, 1922, p. 107CrossRefGoogle ScholarPubMed; Shull, G. H., Harper, R. A., and others, “The Species Concept, etc.“: Amer. Journ. Botany, x, 1923, p. 221CrossRefGoogle Scholar; Vavilov, N. I., “The Law of Homologous Series in Variation”: Journ. Genetics, xii, 1922, p. 47.CrossRefGoogle Scholar