SCIENCE-GOSSIP. 



173 



■also have something tn <lo with tht- colcmr. It may 

 be notid that the sloncchal and whinchat, which feud 

 chiefly 1 in worms, have bhiish green c-i;gs. It seems 

 that vegetable matter and worms supply more carbon 

 and hydrogen than insects, and the latter more iron. 

 There arc many birds that eat largely of insects, 

 seeds, and worms, whose eggs are midway in colour 

 between those of classes I and 2, the eggs being 

 iisunlly light green or blue, and spotted, the family 

 Alaudidae being a good example. 



We now come to Class 3, the sea-birds, and these 

 may be divided into three sections, according to the 

 colour of their eggs : (<!) those which lay buff or 

 stone-coloured eggs, with often darker blotches ; (/<) 

 those with white eggs ; and (c) with greenish eggs, 

 often with dark markings. 



In the first section (a) are the gulls, most terns, 

 divers, the turnstone, oyster catchers, and m.iny others. 

 This colour of the eggs is probably due to a deposit of 

 ■chloride of iron. The chlorine is cert.iinly a very 

 likely waste product from a diet of fish. Why some 

 sea-birds should lay buff or stone-coloured, and others 

 white eggs, is rather a difficult question to answer. 

 It may be noted, however, that most of those species 

 which lay white eggs have dark plumage, such as the 

 petrels and shearwaters. These being nocturnal, or, 

 at least crepuscular in habits, the dark pigment is 

 more useful in the plumage to render its wearers 

 inconspicuous, than it would he on the eggs. 



The green colour of some .sea-birds" eggs (/>) is very 

 <lifferent to that of Class 2. I have never known it 

 to fade in the light, and it takes much more heat to 

 destroy. It certainly contains .sulphur, a kind of 

 sulphide of iron, allied to "green vitriol." It will 

 be found that if a thick .shelled egg, which will not 

 ■easily crack, such a> a guillemot's, is heated by a 

 spirit lamp or candle flame, it gives out an unmis- 

 takable smell of sulphur, quite different to the smell 

 of the other classes of eggs when similarly treated. 



The eggs (i) of the slone petrel, Wilscm's petrel, 

 forked-tailed petrel and fulmar, form a very interest- 

 ing exception to the general colouration of ,sea birds' 

 eggs, as they are white spotted with red. It will be 

 found that these birds are very fond of eating any fatty 

 matter they find floating on the water. I believe this 

 to be another case of carbonate of iron, the carbon 

 being derived from the fat. The three petrels are also 

 nocturnal dark-coloured birds, which accounts for the 

 white ground colour of the eggs. 



The 4th class is a miscellaneous group of birds 

 feeding on various substances containing little of the 

 elements that go to form the pigments of eggs, such 

 as fish and other animals inhabiting fresh water ; so 

 their eggs are naturally white. Among these are the 

 dipper, kingfi.sher, little bittern, little grebe, red- 

 necked grebe, and the families Strigidae, \ulturidae, 

 .etc. The Egyptian vulture is about the only one of 

 its family whose eggs are always marked with reddish 

 spots, but it feeds largely on vegetable refuse. 



The 5th class, the family Falconidae, forms really 

 an exception to the last one, as its members feed on 

 other birds and small mammals. Vet, most of their 



egg'i are spotted or stained red, a pigment very 

 difficult to rub off, and (|uite different to that of 

 the first class. I believe the red colour to be simply 

 an oxide of iron, very likely the result of their diet. 



In conclusion, it will be seen that I have considered 

 most of the colours of eggs to be caused by the 

 union of the iron in the birds' blood, with extraneous 

 matters also present. They may all be said to be 

 derived from impure hacmeoglobin. I will here 

 draw attention to the fact that though the eggs of 

 allied genera are usually similarly coloured, yet 

 this is generally because such allied birds have 

 similar foods, such as the tits and finches. 

 Where there is a difference of food, even in 

 closely-connected species, the colouring of the eggs 

 is different. For instance, among the Turdinae, those 

 birds which eat chiefly seed, fruit, worms and snails, 

 such as the blackbird and stonechat, have blue eggs, 

 while tho-se that feed chiefly on insects have white eggs, 

 spotted red, such as the robin. The terns are a very 

 striking example of this theory ; they can be divided 

 into two classes, those feeding on land insects, fresh- 

 water fish, vegetable matter, worms, or amphibians, 

 and those which eat marine fish. In the first cl.ass 

 are the black tern, white-winged black tern, 

 whiskered tern and gull-billed tern. In the second 

 are the Caspian tern, Sandwich tern, roseate tern, 

 common tern, little tern, sooty tern, and noddy tern. 

 It will be found that the eggs of all in the first-cla.ss 

 are greenish ntarked with brown, and in the second 

 section, stone coloured or buff. 



I think the subject of this article forms a good field 

 for future research. I have merely tried to pi>int 

 the way. 



Norman Court, Soiil/isca, 

 Septciiil'cr $otk, iSgg. 



Gresham Coli,i-;ge Lecturks. — On November 

 14th, 15th, l6th and 17th, the Rev. Professor 

 Edmund Ledger, M.A., F.K.A.S., is intending to 

 continue his course of lectures on sidereal astronomy. 

 The lectures are delivered at the college in Hasing- 

 hall Street, from 6 to 7 p.m., are illustrated with the 

 limelight, and are free. 



Nkwmann's runi.icATlONs. We have received 

 a parcel of the publications issued by Me.ssrs. 

 Newmann and Co., of 84, Newman Street. London, 

 W. Among them are new editions with coloured 

 plates of Slack's " M,-irvels of Pond Life,'' " Beautiful 

 Butterflies," by M. G. Adams, the Rev. W. 

 Ilaughton's "Sketches of British Insects" and the 

 same author's "Country Walks of a Naturalist with 

 his Children." The last three of these books will be 

 attractive to young people, on accoiuu of the 

 brilliancy of their coloured plates, and will be useful 

 in forming a taste for nature's beauties. W'ith regard 

 to the work on Pond Life, there is no better published, 

 and for years past it has been the joy of young 

 microscopists. Newmann's " Hygiene for the School 

 and Home," by II. Major, B.Sc, is a valuable 

 elementar)' work for te.achers in instnicting the young 

 upon the fundamental structure of the body, the 

 treatment of accidental injuries, and other useful 

 knowledge so necessary for the maintenance of a 

 thoroughly healthy constitution. " Hand and Eye " 

 is the firm's monthly magazine on kindergarten work. 



