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change of colour in a negro, who, from repeated attacks of ague, was completely converted to a white man, retaining the characteristic features and hair of an Ethiopian. This change was accompanied with a great sensibility in the skin to the heat of the sun and of fire. In the course of a few months the natural colour returned, first in patches which presented a singularly mottled appearance, and ultimately the former black hue was thoroughly restored to both skin and hair.

We have stated that the Pigment-cells are usually polygonal; but this is not always the case, as is illustrated in the frog, where the cells of the choroid coat vary very much, and in its skin are curiously stellate. The production or intensity of Pigment would seem to be greatly influenced by the sun's light and heat, a removal from such agencies speedily enabling the skin to regain its former colour, as is evidenced by the departure of freckles or browning after a few weeks' return from the exposure to them. Little appears to be known of the chemistry of animal Pigments, but their chief constituent is supposed to be carbon. In a beautiful German preparation of a section of the human chin now before us, not only are the hair-follicles and sudoriparous glands plainly discernible, but also the Pigment-cells in the stumps of hair, which have been cleverly sliced by the skilful operator. An experienced writer says that the skin must be macerated for some days, when the epidermis can be removed and examined with the under-surface uppermost. If it be that of a negro, or any other dark-skinned race, the Pigment-cells will be very distinctly seen by transmitted light. But as negroes are not within the reach of every microscopist, we must in this country be content to purchase a good specimen, readily mounted, from one of our well-known mounters. The eye of the ox yields an excellent object for examination, as the choroid membrane can be easily put up in glycerine, and mounted in a shallow cell.

Whilst taking a stroll with my family, in the month of July, during last summer, along the banks of the Dodder, at Milltown, near Dublin, at which time the water is very shallow in certain parts of that river; and as I am generally on the look-out for objects of natural history, as well to impart instruction to the young folks, as to add to my own imperfect stock; on looking into the water I observed, at its margin, an extraordinary hair-like creature swimming rapidly with graceful and sinuous motion like a miniature eel. It immediately struck me as being the Gordius aquaticus, or Hair-worm, although I had never seen one before.

It was easily captured; and on removing it from the water evidently disliked the change, becoming more rigid, and when held between the fingers appearing as if in much distress, writhing about, and, displaying great elasticity, it made an attempt to tie itself up into a kind of true lover's knot, such as would perhaps, if it had not uncoiled itself again, have puzzled even the Davenport Brothers to unravel.

Being provided with an open-mouth jar of water, on returning home it was transferred to a glass globe, in which were some other fresh-water objects. Its restricted domains, or change of diet, did not, however, appear to agree with it; and after a few days it died before I could observe any change in its appearance. It is said in the early stage of its life to live parasitically in insects.

I obtained a second specimen from a moist place, where there was little or no running water, on the side of Carrick Mountain, near Rathdrum, in the county of Wicklow. I was searching for Cambrian fossils at the time, and on taking up a loose piece of slate to examine it, found, instead of the Oldhamia, one of these remarkable filiform worms. I kept this alive for some days, and on taking it to our Natural History Society, a young medical friend, who is doing good work in the investigation of entozoa and parasitic animals, took a fancy to it, and it was transferred to him.

There is a popular notion amongst boys, which probably arose from seeing this hair-like worm in motion, that if a horse-hair is put into water, and left there for a few days, it will turn into an eel.

These worms, although placed with the Nematoïdea, are distinguished from them by their structure, and especially by the absence of a posterior aperture in the intestinal canal; they are included in the genus Gordius L., and are thus characterized:—head rotund, mouth none, or not distinct, tail of male bifid, and female rounded; its length is from 7 to 10 inches, and its thickness scarcely half a line. It is represented on the woodcut of the natural size, and shows the power it has of coiling itself up.

The feeling of our dignity and our power grows strong when we say to ourselves, My being is not objectless and in vain; I am a necessary link in the great chain, which, from the full development of consciousness in the first man, reaches forward into eternity.—Hyperion.