[7] I am not aware that the details of this striking case have ever been worked out. It should be noted that the green and blue forms are not due to simple modification of the red pigment; for these colours, due to interference, fork over the area occupied by the red lines. The distinctions between these forms cannot therefore be simply chemical, as we may suppose them to be, for instance, in the case of many red and yellow forms, and the genetic relationships of the _Heliconid_ varieties would raise many novel problems and be well worth studying experimentally. [8] Woodeforde, F. C., _Trans. North Staffordshire Field Club_, XXXV, 1901, Plate. [9] E. Gallé, _Compte Rendus du Congres Internat. de Bot. a l'Expos. Univ._, 1900, p. 112. [10] Flora of Mentone, 1864-8, _Nova Acta Acad. Caes._, XXXV, 1869. [11] I owe these facts to Canon A. M. Norman, who showed me illustrative specimens. They were originally described by Bowerbank (_Monogr. Brit. Spongiadae_, vol. II, pp. 18 and XX; vol. III, Pls. I and III). A specimen of _G. compressa_ measured 5 inches, with a greatest width of 3-1/4 in. _G. ciliata_ was found measuring 3 in. long and 3/4 in. wide. These dimensions are many times those of normal specimens. [12] Coutagne, G., _Recherches sur le Polymorphisme des Mollusques de France_, _Annales Soc. d'Agric. Sci. et Industr. Lyon_, 1895. [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. [23] Such direct action has of course been proved to occur in the case of several dimorphic larvae (_e. g._, _A. betularia_, itself) and pupae. [24] See Harris, _Proc. Ent. Soc. London_, 1904, p. lxxii, and 1905, p. lxiii; also Hamling, _Trans. City of London Ent. Soc._, 1905, p. 5. [25] I am indebted to Mr. Outram Bangs of the Harvard Museum for calling my attention to this remarkable case. [26] _Auk_, 1889, VI, p. 219. [27] _Ann. N. Y. Acad. Sci._, 1878, I, p. 149.