The rarity of such illustrative cases is, I believe, more apparent than real. It is probably due to the extreme reluctance of systematists to admit that such things can be, and of course to the almost complete absence of knowledge as to the genetic behaviour of wild animals and plants. Only in such examples as this of the _Coereba_, where colour constitutes the sole difference, or that of the moths which have been minutely studied by many collectors, does the significance of the facts appear. The arrangement of catalogues and collections is such that much practical difficulty of a quite unnecessary kind is introduced. For example, in this very case of _Coereba_, I find the British Museum has a fine series from Grenada including 3 normals and 11 black, and also 16 blacks from St. Vincent. If the black specimens from Grenada were put with the normals which are almost certainly nothing but a recessive form of the same bird, the variation would strike the eye on even a superficial glance at the drawer. But following the notions so naively expressed in the passage quoted above from W. N. Lawrence, the blacks from Grenada are put apart together with the other blacks from St. Vincent, though two of them were shot on the same date as one of the normals. FOOTNOTES: [1] For the evidence see Tutt, J. W., _Trans. Ent. Soc._, 1898, p. 17. Compare the remarkable case given by Gulick (_Evolution Racial and Habitudinal_, p. 123) of the two races of _Cicada_, which are separated by reason of their life-cycles, one having a period of 13, the other 17 years. [2] For references see _Materials_, p. 396, and also G. Baur, _Amer. Nat._, 1893, July, p. 677. [3] Jenner Weir, _Entomologist_, 1880, XIII, p. 251. [4] Jentink, _Notes Leyden Mus._, 1885, VII, p. 111. Specimens illustrating this peculiarity are in the British Museum. [5] _Proc. Zool. Soc._, 1895, p. 850. Plate. Many points beyond that mentioned above are involved in this remarkable case. For example, not only are there males like females, but a small proportion of females resemble the ordinary male type. The stripes are not merely the spots produced, for they occupy different anatomical positions. The spots almost always go with a black ventral surface, but the striped forms nearly always have that region testaceous. _Spartium retama_, the food-plant, will not grow in England, but if it could be naturalised in America the whole problem might be investigated there and results of exceptional interest would almost certainly be attained. [6] Doncaster, L., _Proc. Zool. Soc._, 1905, II, p. 528.