[44] With reference to this subject, see the discussion by the Belgian Entomological Society, Brussels, 1873.
[45] P. E. Müller, “Bidrag til Cladocerners Fortplantingshistorie,” 1868.
[46] Sars, in “Förhandlinger i Videnskabs Selskabet i Christiania,” 1873, part i.
[47] [Eng. ed. Recent researches on alternation of generation in the Daphniacea have convinced me that direct action of external conditions does not in these cases come into consideration, but only indirect action.]
[48] See my memoir, “Über Bau und Lebenserscheinungen der Leptodora hyalina,” Zeitschrift f. wiss. Zool., vol. xxiv. part 3, 1874.
[49] Stettin. entom. Zeit., vol. xviii. p. 83, 1857.
[50] Compt. Rend., vol. lxxvii. p. 1164, 1873.
[51] [“Accidental” in the sense of our being in ignorance of the laws of variation, as so frequently insisted upon by Darwin. R.M.]
[52] [Eng. ed. Since this was written I have studied the ornamental colours of the Daphniidæ; and, as a result, I no longer doubt that sexual selection plays a very important part in the marking and colouring of butterflies. I by no means exclude both transforming factors, however; it is quite conceivable, on the contrary, that a change produced directly by climate may be still further increased by sexual selection. The above given case of Polyommatus Phlæas may perhaps be explained in this manner. That sexual selection plays a part in butterflies, is proved above all by the odoriferous scales and tufts of the males discovered by Fritz Müller.] [For remarks on the odours emitted by butterflies and moths, see Fritz Müller in “Jena. Zeit. f. Naturwissen.,” vol. xi. p. 99; also “Notes on Brazilian Entomology,” Trans. Ent. Soc. 1878, p. 211. The odoriferous organs of the female Heliconinæ are fully described in a paper in “Zeit. f. Wissen. Zool.,” vol. xxx. p. 167. The position of the scent-tufts in the sphinx-moths is shown in Proc. Entom. Soc. 1878, p. ii. Many British moths, such as Phlogophora meticulosa, Cosmia trapezina, &c. &c., have tufts in a similar position. The fans on the feet of Acidalia bisetata, Herminia barbalis, H. tarsipennalis, &c., are also probably scent organs. A large moth from Jamaica, well known to possess a powerful odour when alive (Erebus odorus Linn.), has great scent-tufts on the hind legs. For the application of the theory of sexual selection to butterflies, see, in addition, to Darwin’s “Descent of Man,” Fritz Müller in “Kosmos,” vol. ii. p. 42; also for January, 1879, p. 285; and Darwin in “Nature,” vol. xxi. January 8th, 1880, p. 237. R.M.]
[53] Nägeli, “Entstehung und Begriff der naturhistorischen Art,” Munich, 1865, p. 25. The author interprets the facts above quoted in a quite opposite sense, but this is obviously erroneous.