[10] Conceivably however it may be a segregated combination. For an account of this plant see Boissier, _Voy. Bot. Midi de l'Espagne_, 1839, II, 722. [11] A discussion of this subject with references to literature is given by Rolfe, in an excellent paper on "Hybridisation viewed from the standpoint of Systematic Botany" (_Jour. R. Hort. Soc._, XXIV, 1900, p. 197). He concludes: "The simple fact is that the two plants (_L. diurna_ and _vespertina_) are thoroughly distinct in numerous particulars, and affect such different habitats that in some localities one or the other of them is completely wanting. But when their stations are adjacent they hybridise together very readily, and it is here that these intermediate forms occur which have puzzled botanists so much." The same paper contains valuable information concerning several cognate illustrations. [12] In only two cases have I seen such plants (both females) completely sterile. [13] As is well known, in an even more notorious example, he proposed to unite _Primula vulgaris_, _P. elatior_, and _P. acaulis_, similarly relying on the existence of "intermediates," which we now well know to be mongrels between the species. [14] For an account of the distinctions between _Vespa vulgaris_ and _germanica_ see Ch. Janet, _Études sur les Fourmis, les Guêpes et les Abeilles_, 11^e, Note. Sur _Vespa germanica_ et _V. vulgaris_. Limoges (Ducourtieux), 1895; and R. du Buysson, Monographie des Guêpes, _Ann. Soc. Ent. France_, 1903, Vol. LXXII, p. 603, Pl. VIII. [15] The statements made above are for the most part taken from Barrett, C. G., _Lepidoptera of the British Islands_, and from Tutt, J. W., _The British Noctuae and their Varieties_. The reader who is unfamiliar with the amazing polymorphism exhibited by some of these moths should if possible take an opportunity of looking over a long series in a collection, or, if that be impossible, refer to the admirable coloured plates published by Barrett. It may not be superfluous to observe that plenty of similar examples are known in other countries. For instance _Plotheia frontalis_, a Noctuid which often abounds in Ceylon, shows an equally bewildering wealth of forms. If a dozen specimens of such a species were to be brought home from some little known country, each individual would almost certainly be described as the type of a distinct species. (See the coloured plate published by Sir G. Hampson, Cat. Brit. Mus., Heterocera, Vol. IX.) [16] _Dict. of Birds_, p. 800. It would be interesting and profitable to attempt in a long series of Ruffs to determine the Mendelian factors which by their combinations give rise to this complex assemblage of varietal forms. A few such factors both of colour and pattern can be at once distinguished, and it is noticeable that some of the resulting types of barring, spangling and penciling show a perceptible correspondence with some of the types of colouration found in the breeds of domestic fowls.