hood of Pitlessie, in Fife, and had three of his men along with him. They wrought in a cart-shed, which they had used for some time as their workshop; and one morning they observed a mavis (thrush) enter the wide door of the shed, over their heads, and fly out again after a short while; and this she did two or three times, until their curiosity was excited to watch the motions of the birds more narrowly; for they began to suspect that the male and female were both implicated in this issue and entry. Upon the joists of the shed were placed, along with some timber for agricultural purposes and old implements, two small harrows, used for grass-seeds, laid one above the other; and they were soon aware that their new companions were employed with all the diligence of their kind in making their nest in this singular situation. They had built it, he said, between one of the butts of the harrow and the adjoining tooth; and by that time, about seven o'clock, and an hour after he and his lads had commenced their work, the birds had made such progress, that they must have begun by the break of day. Of course, he did not fail to remark the future proceedings of his new friends. Their activity was incessant; and he noticed that they began to carry mortar (he said), which he and his companions well knew was for plastering the inside. Late in the same afternoon, and at six o'clock next morning, when the lads and he entered the shed, the first thing they did was to look at the mavis's nest, which they were surprised to find occupied by one of the birds, while the other plied its unwearied toil. At last the sitting bird, or hen, as they now called her, left the nest likewise; and he ordered one of the apprentices to climb the baulks, who called out that she had laid an egg; and this she had been compelled to do some time before the nest was finished; only plastering the bottom,

very little different from those of the wren or the haybird (Sylvia Trochilus), which build covered nests with a small side entrance; while the house-sparrow (Passer domesticus, RAY) lays eggs of dull greenish or bluish-white, streaked with greyish-black, and always builds in holes or under cover.

As these objections appear to be unanswerable, it will not be necessary for us to follow Dr. Darwin into his fanciful account of the origin of the colours of eggs, which he ascribes to the colour of the objects amongst which the mother-bird chiefly lives, acting upon the shell through the medium of the eye; for if this were correct, we should have the green-finch and the red-breast, instead of their white eggs, laying blue ones, like the red-start.

In the case of the eggs of insects, the colours are sometimes, though not in every instance, occasioned by the colours of the embryo shining through the shell, an example of which we have in the small rhinoceros beetle (Oryctes nasicornis, ILLIGER *). In birds, however, this never occurs; and the markings on the eggs seem, so far as we can perceive, to have no connection with the colours and shadings on the feathers. Birds, indeed, of the most varied plumage, such as the peacock and the humming-bird, are produced from white eggs. It is reasonable to conclude, however, that these colours and markings on eggs are intended to serve some particular purpose, though we may not, in the present state of our knowledge, be able with certainty to say what.

Without advancing any theory as to the cause of the phenomenon, Mr. Griffiths has deduced some general inferences from the facts in a more cautious way than Darwin and Glöger. "The eggs," he remarks, "of diurnal birds of prey are of a whitish colour, spotted with red, or red spotted with brown. *Insect Transformations, p. 36.

(Muscicapa nunciola), and a few others, employ a portion of masonry either on the outside or in the middle of their nests; but the material used being chiefly mud, or clay, the workmanship is rude and unfinished when compared with the neat execution of the song-thrush. In the case of the blackbird, the outer frame-work differs little from that of the song-thrush, except perhaps in being more massive, as is also the clay lining, which is put on in a very wet state, probably to save the saliva of the bird. But to prevent this moisture from injuring the eggs, it is lined with a thick bedding of dry hay, which in some nests is very neatly worked into the hollow formed by the clay, while in others it is laid less skilfully, and hence renders the nest very shallow. Syme is wrong, therefore, in saying the nest is

greenish, or yellowish ground. It is remarkable that the eggs which certain species deposit on green herbs partake more or less of this colour. The passeres have eggs, the ground of which is white or whitish, blue or bluish, green usually spotted with deep colours, such as red, brown, and black. The tom-tit kind, which nestle in the hollows of trees, have eggs altogether white, or white picked with red. The same is the case with the swallows and martins. The larks, pipits, &c. have the eggs of an earthy hue *."

*Cuvier's Animal Kingdom, Aves, i. 138.

CHAPTER VIII.

FACTS OBSERVED IN HATCHING.

Ir is indispensable to hatching, that an equable temperature be kept up of about 96° Fahr. or 32° Réaum., for at lower temperatures the living principle appears to become torpid and unable to assimilate the nourishment provided for developing the embryo. Proceeding upon this principle, the Egyptians, as well as those who have tried the experiment in Europe, have succeeded by means of artificial heat in hatching eggs without any aid from the mother birds.

One of the most remarkable stories respecting artificial hatching is that arising out of a girlish superstition of the Roman Empress Livia. The tale is told by Pliny: "She took an egge, and ever carried it about her in her warme bosome; and if at any time she had occasion to lay it away, she would convey it closely out of her own warme lap into her nurse's for fear it should chill*." M. Réaumur mentions some modern instances of a similar kind: "One lady hatched four goldfinches out of five eggs from the same nest; one of the eggs having proved a rotten one, she was obliged to keep them warm only for ten days. Another lady," he adds, "told me a more extraordinary, though by no means an incredible fact of the same kind, assuring me she had seen a female lap-dog sit on eggs quite

Holland's Plinie, x. 55.