Materials for the Study of Variation Treated with Especial Regard to Discontinuity in the Origin of Species

Intermediates between edusa and helice must be exceedingly rare. OBERTHUR records two such specimens and says that STAUDINGER took a similar one at Cadiz. For this intermediate he proposes a new name, helicina. Bvill. Soc. Ent. Fr. (5), x. p. cxlv. 1 In this case I can affirm the alternative character of the inheritance. For several years a pair of swans kept by St John's College, Cambridge, have produced cygnets, some of which have been of the normal grey, while others have been fawncolour, a condition which Prof. Newton tells me has been thought characteristic of the "Polish" swan, a putative species. None of these cygnets are intermediate in colour, and all acquire the full white adult plumage, but the feet of the fawn-coloured cygnets remain pale in colour. Now the father of these has pale feet and was doubtless himself a fawn-coloured cygnet ; the hen is normal. The cock formerly belonged to Dr (iifford, who kindly told me that the cygnets of this bird by a different hen were also thus diverse. A pair of these were given to Sir John Gibbons, who informs me that " from these there has been a brood every year, and always I think one of the cygnets has been white or nearly so, the others being of the usual colour." One of I)r Gifford's birds was also given to the late Mrs Gosselin of Blakesware, to whom I am indebted for descriptions of and feathers from several fawn-coloured cygnets which were its offspring. A similar case on the Lake of Geneva is recorded by FAUVEL, Rev. ZooL, 1869, p. 334, and another in the Zool. Gardens at Amsterdam, by NEWTON, Zool. l\ec., 1869, p. 99.

a This is well known to collectors of fresh-water fauna, and I have repeatedly seen the same phenomenon in species of l)iapto»nts, especially I), aniuticua, in the lakes of W. Siberia. Among thousands of individuals with red-brown egg-sacs, will often occur a few specimens having the egg-sacs of a brilliant turquoise-blue. In this connexion compare the case of the Crayfish (Antaeus jiuviatilis), which turns scarlet on being boiled, and which, like the Lobster, not uncommonly appears in a full blue variety.

3 Culoptrinis nprftus with hind tibiir blue instead of red, DODGE, Can. Ent., 1878, x. p. 105 ; Melitnopliix pticliurtlii, having hind tibiie red instead of bluish, BKONER, Can. Ent., 1885, xvn. p. 1H. For reference to these observations I am indebted to COCKERELL, Knt., IHH',1, xxn. p. 127. * WHITE, Ent., 188K, xxn. p. 51. Compare the fact that in another species of Catocala (C.fraxini), the Clifden Nonpareil, the hind wings are normally bluish.

A curious specimen, apparently a male, having the colour of helice was kindly shewn me by Mr F. H. WATERHOUSE. The light marks which in the female are present on the dark borders of the fore-wing are only represented by one minute light mark on each fore-wing. In most if not all of the edusa group of Colias, there is a pale aberration of the female, corresponding to the helice variety of e<ln««. ELWES, Tr. Ent. Soc., 1880, p. 134. In the same paper is a full account of the geographical distribution of the several species and colour-varieties of Colias.

Colias hi/ale (Pale Clouded Yellow) is normally sulphur-coloured. Nearly white varieties and a variety with the field rich sulphur colour, and the apical marginal patches red, are recorded in several works. 2. Gonepteryx rhamni (The Brimstone) is sulphur-yellow in the male, and greenish-white in the female. There is a spot in each wing, and the scales covering this on the upper side are bright orange. Gonepteryx cleopatra, a S. European species, is like the above in the hind-wings, while the field of the fore-wings is flushed with orange of exactly the tint of that on the spots of G. rhamni.

There are several records in entomological literature alleging the capture of "G. cleopatra" in Britain, e.g. Proc. Ent. Soc., 1887, p. xliii. In addition to these there are records of specimens of G. rhamni more or less flushed with orange ; e.g., a specimen at Aldershot with orange spots on fore-wings as in cleopatra, Proc. Ent. Soc., 1885, p. xxiv. Mr Jenner Weir said he had seen a specimen in Ingall's collection, intermediate between rhamni and cleopatra. ibid.

A male of G. rhamni taken at Beckenham had the costal margin of each fore-wing broadly but unequally suffused with bright rosecolour or scarlet, and the right posterior wing was marked in like manner. The insect was thus marked when captured. BICKNELL, Proc. Ent. Soc., 1871, p. xviii. 3. Anthocharis (Euchloe) cardamines (The Orange Tip), in the male has the foi'e-wings tipped with orange on both sides, while in the female these orange tips are absent. The field in both is white. In entomological literature are many records of variations in the extent and depth of the orange markings on upper or under side, or both (cp. Zoologist, xiii. 4562; Proc. Ent. Soc., 1870, p. ii. ; MOSLEY, Illustrations of British Lepidoptera ; HAWORTH ; BOISDUVAL and many others), but with these we are not immediately concerned.

A specimen is figured in which the orange spots were completely represented by yellow. MOSLEY, Illustrated Brit. Lep. The white of the field is replaced by primrose or lemon yellow in several Continental forms. These have been described as species under the names eupheno, belia, eit/jhenoides, gruneri, &c. A local variety of A. eupheno is described from Mogador, where it was found common at a little distance from the town. The female was much larger than the type, resembling the male in markings and in shape of the fore-wings. The orange blotch, instead of being confined to tip of the fore-wing as normally, extends to the discoidal spot and is usually bounded by a black band, sometimes suffusing the whole tip of the wing. The colour of the field varies from pure white to pale lemon : the hind-wings are always yellower than in the type, in some

specimens being nearly as yellow as those of the male. Mr M. C. Oberthur supplied a specimen from Central Algeria which was interinciliate between the type and this variety. LEECH, J. H., P. Z. S., 1886, p. 122. 4. Amongst Lepidoptera the change from red to yellow is very common. A case of Vam-sxn atdlauta, having the red partially replaced by yellow, is figured in /,'///"///., 1878, xi. p. 170, Plate. Varieties of Arctia caja, CallimorpJui dominula, C. Jtebe, C. hera, C. jacoboew, /t//:/rena Jilipendidce, Z. minos, tic., with yellow instead of red, are to be seen in many collections. See especially OCHSEXHEIMER, tichm. v. Europa, 1808, II. p. x, also p. 25, and many other authors. A chalk-pit at Madingley, Cambridge, has long been known to collectors as a locality for the yellow Z. filipendulce (Six-spot-Burnet); see Ent. M>i. ^[<l(|. xxv. p. 289. In some of these the yellow is tinged with red, but it is commonly a very distinct variety. A variety of the Red Underwing ((_'nf«fiiln nupta) with brownish-yellow in the place of the red, is figured by ENQRAMELLE, Papill. d'Eur., PI. cccxxn. The evidence relating to this subject is very extensive, and concerns many genera and species besides those named above.

5. Pericrocotus flammeus (an Indian Fly-catcher) is grey and yellow in the female, and black and orange-red in the male. The young male is grey and yellow like the female. An adult male is described in which the grey had been fully replaced by black, but the yellow remained, not having been replaced by red. R. G. WARDLAW RAMSAY, P. Z. .S'., 1879, p. 765. See also LEGGE, Birds of Ceylon, i. p. 363, for description of male in transitional plumage. Curiously enough the change from red to yellow and from light yellow to dark is no less common among plants, though it can scarcely be supposed that the substances concerned are similar.

1. Narcissus corbularia and other species are known in sulphuryellow and in full yellow1. 2. The Iceland Poppy (P. nudicaule) is very common in gardens under three forms, white, yellow and orange. Intermediate and flaked varieties occur, but are less common than the three chief forms. Respecting this species Miss Jekyll of Munstead, who first brought out the varieties, kindly gives me the following information. She writes : — " I began with one plant of the yellow colour that I take to be the type-colour. It was then new as a garden plant, so I saved the seed. The first sowing gave me various shades of orange, as well as the type, in different shades. In the 3rd and 4th years I got buffs, whites, and very pale lemon colourings. As there was only one plant to begin with there was no question of cross-fertilization. A white appeared in

the 3rd year of sowing and I kept on selecting for 2 or 3 years and gave it to a friend in Ireland, who returned it to me 2 years later still more improved. This strong white seems now to be fixed and quite unwilling to revert to the yellow colourings, and is a rather stouter and 1 Mr P. Barr, who has collected these forms in Portugal, tells me that he believes the pale ("citrina") varieties of .V. ujax and .V. corbularia to be confined to calcareous soils.

handsomer plant altogether." In seedlings from the orange or yellow form grown in separate beds the proportion of seedlings true to their parent colour would not be nearer than about 60 or 70 per cent., but in the case of the white form Miss Jekyll considers that 95 per cent, may be expected to come true. The yellow Horned Poppy (Glaucium lute um) is normally of a lemon yellow very like that of P. nudicaule. Of this species also there is an orange cultivated variety. The varieties of the tomato offer a similar series of colour-variations.

3. Fruits of many kinds are known in red and yellow forms. For instance the yellow berried Yew is well known. It is described under the name Taxus baccata fructu-luteo, LOUD. "It appears to have been discovered about 1817 by Mr Whitlaw of Dublin, growing in the demesne of the Bishop of Kildare, near Glasnevin; but it appears to have been neglected till 1833 when Miss Blackwood discovered a tree of it in Clontarf churchyard near Dublin. Mr Mackay on looking for this tree in 1837 found no tree in the churchyard, but several in the grounds of Clontarf Castle, and one, a large one, with its branches overhanging the churchyard, from which he sent us specimens. The tree does not differ, either in its shape or foliage, from the common yew, but when covered with its berries it forms a very beautiful object, especially when contrasted with yew trees covered with berries of the usual coral colour." LOUDON, Arb. et Frut £rit., iv. 1838, p. 2068.

4. The Raspberry (Rubus idieus) is another fruit which is known wild in both the red and yellow forms, though the latter is less common. According to BABINGTON, it has pale prickles, and leaflets rather obovate. Brit. Jtubi, p. 43. (See RIVERS, Gard. Chron., 1867, p. 516.) Any person who has opportunities of handling animals and plants in numbers can add many similar cases. These few are taken more or less at random, as illustrations of the frequency with which red, orange, and yellow may vary to each other. It is of course not necessary to say that in numerous instances both among animals and plants, the same parts which in one species are yellow, in an allied species or in a geographically distinct race are represented by orange or by red. To an appreciation of the rapidity with which such changes may have come about, facts like the foregoing contribute.

The frequency of such variations suggest that many of these yellow and red pigments are either closely allied bodies or different forms of the same body. Until the chemistry of these substances has been properly investigated nothing can be definitely stated as to this, but the fact that vegetable yellows are very sensitive to reagents is familiar. The lemon variety of the Iceland Poppy treated with ammonia turns to a colour almost identical with that of the orange variety, while the white variety so treated goes primrose yellow. The lemon variety when boiled, or treated with alcohol yields an orange solution, which is of the same tint. This returns to lemon-colour if treated with ammonia or acids. The

win^s of G. rftawni when boiled yield a soluble yellow, which 1 1. .I-KIXS (Proc. Cliem. Soc., reported Nature, Dec. 31, I vi | . 'is ;i .l.-rivativo of mycomelic acid, allied to uric acid. This substance turns orange with reagents. The wings of G. rhwtmi turn orange-red when exposed to wet potassium cyanide (Proc. i: • - |s71. ],. \\iii) as may be easily seen. \Vh.-n these facts, meagre though they are, are considered ,ith the evidence of variability, the suggestion is very that the discontinuity between these several eharac- > of a chemical nature, and that the transitions i one -hade of yellow to another, or from yellow to orange or i phenomenon comparable with the changes of litmus and •able blues from blue to red or of turmeric from v,-i: bi..\\n. If such a view of these phenomena were to be

• I. it would. I think, be simpler to regard the constancy of th,. binta »t the several species and the rarity of the intermediate \:u . direct manifestation of the chemical stability or iliilitv of the i-.. louring matters, rather than as the conof environmental Selection for some special fitness a^ t.i \\li.is,- nature we can make no guess. For we do know the phenomenon <.f chemical discontinuity, whatever maybe its ultimate causes, but ..f tin — - hypothetical fitnesses we know nothing, n..t . \.-n whether they exist or no.

II. C«/'»<r-i>'ift<'/-/i*. Thus far I have spoken only of discontinuous v:iri:iti'>ns in colours themselves, but there are no less remarkable instance, , ,f i U.-M-. mt iuu« in^ variations in the distribution <if i-.ili.urin partiri.louivil t'oi-ms. By a combination of tli.-.- in. •.!,•-. variation- «>f ^r> at magnitude may occur. ()M.- ..f th.- most obvi,.u- cases of this phenomenon is that of the ('at. In Km-.. ]•• an towns cats anof many colours, but they ii.-\.-rtl1(-l.-- fall very n-adily into c.-rtain classes. The chief of tli. -•• are Mack, tabby, silver-grey and silver brindled, sandy, tortoi-,, -h.-ll. black and white, and white. ( )f course no two cats hav.- id.-iitical ciilnirini,', but the individual variations group very

;lv round these Centres, and intermediate forms which cannot at -"mi-tiling out of the common and ^tran^e. Vet it is almost certain that cats ..fall shades l.re.-d freely together, and there is no r.-a^..ii to viij,|,,,-e that the discontinuity lietwecn the colour- •u|>- i> in any way (let.-i-miiied by Natural Selection. Aiiot! mple ma\ be aeen in the hog-whelk (I'm-punt ln/n/liiM). Tinanimal OCCUTS on nearK the whole British coast. h locality dilV-T more or |e<s from those of other localities, and

of calcification, amount nt •' frilling." vVc. The peculiarities may be so striking that each individual can at once be recognized as belonging to a given locality, or they may be trifling, and appreciable only when a large number of individuals are gathered. But apart from these differences of form and texture there are a great number of colour-varieties of which the following are the three chief whole-coloured forms, viz. white, dark purple-brown, and yellow. In addition to these there are banded forms, and the bands may be coloured with any two of the three colours mentioned above. Among the banded forms there are two distinct sorts of banding, in the one there are very many fine bands and in the other there are a few broad bands. In most localities these colourvarieties may all be found ; though in some places, especially where the water is foul, as at Plymouth, the shells are greatly corroded and the colours, if originally present, are obscured. Speaking however of localities in which colourvarieties are to be seen at all, several may generally be found together. If any one will take the trouble to gather a few hundreds of these shells and will set himself to sort them into groups according to their colours, he will find that the majority fall naturally into groups of this kind ; and that those which cannot be at once assigned to groups but fall intermediately between the groups are comparatively few. I have seen this at many places on the English coast; in Yorkshire, Norfolk, Suffolk, Kent, Sussex, Dorsetshire, Devonshire, Cornwall, &c. In several localities I have found pairs belonging to different colour-varieties breeding together, and there is therefore no reasonable doubt that these colourvariations do not freely blend, but are discontinuous.

The statements here made with regard to P. lapillus hold in almost the same way for Littorina rudis, but in this case the number of colour-types is larger. In L. rudis I have occasionally seen specimens of which the upper part belonged to one colourtype, and the lower to another, the transition occurring sharply at one of the varices. In these cases the shell appears to have been injured and is possibly renewed. One of the commonest British Lady-birds (Goccinella decernpunctata) is an extremely variable form. A great number of its varieties may be found together, ranging from forms with small black spots on a red field to forms in which the field is black with a few red spots. But in spite of the great diversity there are certain types which are again and again approached, while the intermediates are comparatively scarce.

The following case, well known to entomologists, may be mentioned here. The Painted Lady (Pyramels cardui) is found in the typical form over the entire extent of every continent, with the exception of the Arctic regions and possibly S. America. A special form of it (var. kershawi) is found in Australia and New Zealand, but the other large islands south of Asia possess the normal type. The latter is also found in the Azores, Canaries, Madeira and St Helena. This butterfly has been taken on the snow-level in the Alps ; and in N. America, though it may be regarded as one of the commonest butterflies in the elevated central district, it is most abundant at a level of 7000 — 8000 feet. It has been taken on Arapahoe Peak, between 11,000

from ScrntiKR, liutttrfliet o/AT. America, i. pp. 477 — 480). Of this .nt one, a certain striking aberration has been found, alw.i -'ity, in many lands. In this aberration the markings are nlm"-t i-ntir. i to have been first described by RAMBCR under ir. 7-. /(/MI, but this description I have never found. (The reference withmit coloured figures description is almost useless, but the .ie very accessible. In a British specimen of this aberration tinwin- t from the anterior costffi and a series of white fusiform

i liiinl wings are equally aberrant. The two large dark spots which are • .'i tin; median nervure and the inner margin are altogether in t)i< ii'irnuil form there is no white spot at all on the hind-wings. These white tinhind-wing! iurm a row parallel to the border of the wing and, as it were, continue the series of white spots borne by the anterior wings. [Underside not described.] This specimen was reared from a larva found near the river Lea, Clapton Park. CLARK, J. A., Entomologist, 1880, xni. p. 73, fig. A. coloured figure of the same specimen, MOSLKY, S. L., PI. 8, Jig. 3.

A form very closely similar to the above is figured in black and white by Newman from a specimen in Ingall's collection (fig. 5, B). [This is apparently the specimen given in Zoologist, p. 3304.] NEWMAN, British Butterflies, p. Qi^ftg. A British specimen which nearly approaches this aberration in the absence of the white bars on the costse and in the absence of the black transverse bar is recorded. In it each of the sub-marginal rows of black spots on the posterior wings is drawn, containing a white spot. In this specimen the brown-red of the type was represented by rose-colour. NEWMAN, Entomologist, 1873, p. 345, fig.

Another specimen closely resembling this aberrant form is described from New South Wales. OLLIFF, A. S., Proc. Linn. Soc., N. S. W., S. 2, in. p. 1250. Another specimen closely resembling the above was taken at Graham's Town, S. Africa, and is mentioned by JENNER WEIR, Entomologist, 188'J, xxn. p. 73. Another specimen is figured in which the hind-wings are marked as in the above, but the anterior wings, though strongly resembling this aberration in the general disposition of the colours, yet differ in details, the chief points of difference being that the white costal bar is only partially obliterated and the white spots on the anal angles of the fore-wings are not developed.

[This specimen was in Kadeu's collection and was presumably European.] HEURICH-SCHAFFER, Bd. i. p. 41, PL 35, figs. 157 and 158. A description is given of an aberrant form taken at King William's Town, S. Africa, which " closely resembled that figured by Herrich-Schitffer." THIMBU, B., South-African Butterflies, i. p. 201. A specimen (British) resembling the above, but lacking the white spots on the anal angles of the forewings and having the marginal row on the hind-wing lightcoloured, but not quite white, is figured by MOSLEY, Pt. in. PI. 3, fig. 3.

Two specimens were taken in New Jersey, U.S.A., which are stated to have conformed to this aberration. STRECKER, Cat. N. Amcr. Macrolepidop., p. 137. Another British specimen generally resembling Herrich-Schaffer's figure is represented by MOSLEY, PI. 8, fig. 4. In all the above specimens the resemblance, as far at least as the upper surface is concerned, is considerable. With the exception of Herrich-Schaffer's example, the undersides are not figured, but from the descriptions it may be gathered that they also resembled each other though probably not so closely as the upper surfaces. The resemblance between the underside of the Australian specimen and that figured by Herrich-Schaffer must have been very close.

"Intermediate between these extreme sports and the normal form are three examples taken at Cape Town in 1866, 1873 and 1874 — the first by myself —in which the fore-wing markings are scarcely affected, but the hind-wing spots are minutely ocellate and externally prolonged, so as to be confluent with the succeeding row of lunules." TRIMEN, ibid. pp. 201, 202. Another aberration, a Belgian specimen, resembles " Elymi" in kind but differs from it in degree. In it also the white bars are absent from the cost®, and the brown and black markings of the anterior wings are rearranged in almost exactly the same manner. The posterior wings are modified to a much less extent and the normal row of black spots between the nervures remains, while only the first and second of the series of white spots is present, the former being very slight. In this individual the markings of the underside also resemble the aberration generally, but it retains the four ocelli of the type. DE DONCEEL, H. DONCKIER, Ann. Soc. <?Ent. Beige, 1878. xxi. p. 10, Plate.