[13] As to the synonymy and references see Coutagne, p. 45.
[14] A. Lang, Die Bastarde von H. hortensis Muller H. nemoralis L. Jena, G. Fischer, 1908; with a fine coloured plate showing the varieties of the species and their hybrids.
[15] With this evidence compare that given by A. Delcourt in his valuable papers lately published relating to the variations of Notonecta. See especially Bull. Sci. Fr. Belg., 1909, XLIII, p. 443; and C. R. Soc. Biol., 1909, LXVI, p. 589.
[16] Allen, J. A., Bull. Amer. Mus. N. H., III, 1891, pp. 51-54.
[17] J. T. Gulick, Evolution, Racial and Habitudinal, Carnegie Institution, Publication No. 25, 1905.
[18] A. G. Mayer, Mem. Mus. Comp. Anat. Harvard, Vol. XXVI, 1902, p. 117. From the tables given I cannot ascertain the actual numbers from the two intermediate valleys, but they were considerable.
[19] To which I was very kindly guided by Mr. C. T. Trechmann.
[20] Standfuss, Handbuch d. paläarkt Gross-schmet, 1896, p. 321.
[21] Ent. Rec., XVIII, No. 7, 1906.
[22] This evidence was largely collected by Mr. G. T. Porritt, who has given much attention to the subject.