[23] In regard to the closely analogous case of _Spilosoma lubricipeda_, Standfuss makes a similar statement. He bred the type on a large scale with the radiate form which he calls _intermedia_, and says that in four years of miscellaneous crossing he never obtained really transitional forms. Nevertheless after examining large series, especially those of Mr. W. H. B. Fletcher, I came to the conclusion that several might be so classed, but I am quite prepared to find that such specimens are heterozygous. (See Standfuss, _Handb. d. Gross-Schmet._, 1896, p. 307.) It is by no means unlikely that various dark forms of _lubricipeda_ correspond with a progressive series of factorial additions. Many of the stages have been named, and of these the most definite are the _intermedia_ of Standfuss (probably = _eboraci_ of Tugwell) and the very dark _Zatima_ of Heligoland, in which only the thorax, the nervures and a small field in the fore-wings remain yellow. A form was bred by Deschange from _Zatima_ in which even the field in the forewing is obliterated. The exact circumstances in which _Zatima_ occurs in Heligoland would be worthy of special investigation, for the normal _lubricipeda_ is also found on the island. For references as to the British occurrences see especially, Hewett, W., _Naturalist_, 1894, p. 353. As to _Zatima_ see especially Krancher, _Soc. Ent._, II, 1887-8, p. 26. I am indebted to Dr. Hartlaub for information as to the Heligoland types. [24] Boisduval, _Bull. Soc. Ent. Fr._, III, 1834, p. 5. [25] The systematics of _Setina_ have been much controverted, but no one I believe doubts that _aurita_ and _ramosa_ are forms of one species. See also Chapman, A. T., _Ent. Rec._, XIII, 1901, p. 139. [26] _Arch. Naturg._, 33, 1867, p. 116. [27] _Brit. Mus. Cat., Batrachia Gradientia_, 1882. [28] The Geographical Distribution of nearly related Species. _Amer. Nat._, XLI. 1907, p. 207. [29] See later, p. 242. CHAPTER IX THE EFFECTS OF CHANGED CONDITIONS: ADAPTATION In the attempt to conceive a process by which Evolution may have come about, the first phenomenon to be recognized and accounted for is specific difference. With that recognition the outline of the problem is defined. The second prerogative fact is adaptation. Forms of life are _on the whole_ divided into species, and these species _on the whole_ are adapted and fit the places in which they live. To many students of Evolution, adaptation has proved so much more interesting and impressive than specific diversity that they have preferred it to the first place in their considerations.