These interesting animals are said to be smaller than ordinary mice, to be usually of a brownish colour, and to have long ears. Naturalists have not come to any exact reason as to why they sing. Some persons impute the singing to disease, as in the wheezing of any one from a cold. Others attribute it to an internal parasite. But these seem unsatisfactory explanations; for when the little creatures sing they are as lively as common domestic mice. The faculty of singing in a small way with various modulations appears to be quite natural to the animals. It has been noticed that during their musical performances there is a throbbing in the throat, and that the snout is elevated in giving play to the voice, as in the warbling of birds. The song or warble of these mice is said to be sweet and varied. Hitherto not much attention has been given by zoologists to the phenomenon; but we observe by various notices in Land and Water and in Nature, two periodicals devoted to pleasant discussions on subjects of natural history, &c., that singing mice are becoming objects of careful investigation.

An amusing account of a singing mouse appears in Nature, Nov. 9, from the pen of Mr Joseph Sidebotham, dating from Menton, south of France.

'Last winter we occupied the rooms we now do at Menton. Early in February we heard as we thought the song of a canary, and fancied it was outside our balcony; however, we soon discovered that the singing was in our salon, and that the songster was a mouse. At that time the weather was rather cold, and we had a little fire, and the mouse spent most of the day under the fender, where we kept it supplied with bits of biscuit. In a few days it became quite tame, and would come on the hearth in an evening and sing for several hours. Sometimes it would climb up the chiffonier and ascend a vase of flowers to drink at the water, and then sit and sing on the edge of the table and allow us to go quite near to it without ceasing its warble. One of its favourite haunts was the wood-basket, and it would often sit and sing on the edge of it. On February 12, the last night of the Carnival, we had a number of friends in our salon, and the little mouse sang most vigorously, much to their delight and astonishment, and was not in the least disturbed by the talking. In the evening the mouse would often run about the room and under the door into the corridor and adjoining rooms, and then return to its own hearth. After amusing us for nearly a month, it disappeared; and we suspect it was caught in a trap set in one of the rooms beyond. The mouse was small and had very large ears, which it moved about much whilst singing. The song was not unlike that of the canary in many of its trills, and it sang quite as beautifully as any canary, but it had more variety, and some of its notes were much lower, more like those of the bullfinch. One great peculiarity was a sort of double song, which we had now and then—an air with an accompaniment. The air was loud and full, the notes being low and the accompaniment quite subdued. Some of our party were sure that there was more than one mouse, until we had the performance from the edge of the wood-basket and were within a yard or two of it. My son has suggested that many or all mice may have the same power, but that the notes are usually so much higher in the scale that, like the cry of the dormouse and the bat, they are at the verge of the pitch to which the human ear is sensitive. This may be so; but the notes of our mouse were so low, and even the highest so far within the limits of the human ear, that I am inclined to think the gift of singing in mice is but of very rare occurrence.'

In the same periodical, the following additional particulars as regards singing mice are presented by Mr George J. Romanes, Regent's Park.

'Several years ago I received some of these animals from a friend, and kept them in confinement for one or two months. The description which your correspondent gives of their performance leaves very little to be added by me, as in all respects this description agrees perfectly with my own observations. I write, however, to remark one curious fact about the singing of these mice, namely, that it seemed to be evoked by two very opposite sets of conditions. When undisturbed, the little animals used for the most part to remain quiet during the day, and begin to sing at night; but if at any time they were alarmed, by handling them or otherwise, whether during the day or night, they were sure to sing vigorously. Thus the action seemed to be occasioned either by contentment or by fear. The character of the song, however, was slightly different in the two cases.

'That these mice did not learn this art from singing birds there can be no doubt, for they were captured in a house where no such birds were kept. It may be worth while to add that this house (a London one) seemed to have been suddenly invaded, so to speak, by a number of these animals, for although my friend has lived in this house since the year 1862, it was only during a few months that singing mice were heard in it, and during these few months they were heard in considerable numbers.'

As corroborative of the foregoing notices, we give the following very interesting account of a singing mouse, obligingly sent to us by a correspondent, Mr Alfred Wright.

'In the early spring of last year I was invited by an old widow lady to see a singing mouse, which she had at night heard singing and scratching beneath the floor of her bed, and been so fortunate as to catch in a trap. I went, and found the little animal in a cage with a revolving wheel, similar to that in which a squirrel is usually confined. Whether the mouse was shy at the presence of a stranger, I do not know. It remained silent; but at length, after my patience had been nearly exhausted, it began to sing in clear warbling notes like those of a bird. When I called the next evening to hear the mouse again, I heard him to perfection; and was so filled with interest in the novelty, that I begged permission to bring any friend who was a sceptic of the fact, or who might desire to see the phenomenon. My request was readily granted. One friend of course had heard of a singing mouse, but he certainly would not allow that a prolonged squeak was a song—not he! Another friend of course had heard a mouse sing when he was a boy; but he was told, he perfectly well remembered, that the noise produced by the mouse was the result of some internal disease. Well, both of these went with me to hear the little creature. Unfortunately, at first it was again shy; but after an interval of silence it commenced to sing—sweetly, like the low notes, the jug, of the nightingale. My friends had come, had heard, and were conquered! The one acknowledged it was really a song and not a squeak; the other, that the noise was certainly dulcet; but still he thought it possibly might be the result of disease, and not natural to the little animal. We suggested that this wonderful natural curiosity (as we deemed it) should be sent to an eminent naturalist who resided near. Great, therefore, was my astonishment and pleasure when it was presented to me, who could only treat it like a schoolboy would his white mouse—as a pet. And truly it became a great pet to both my wife and myself.

'In form, the singing mouse did not differ from his humbler brethren; but in colour he was of a darkish brown, and had very bright eyes. It soon became used to the presence of my wife, and sang constantly while revolving the wheel of his cage. The notes proceeded from the throat. He became exceedingly gentle, and was pleased at being caressed.

'I deemed him so rare a curiosity that I ventured to offer to exhibit him to the distinguished naturalist referred to above, and in my letter described the little creature and its peculiarities, as I have done here. The naturalist most courteously replied: "The case of the singing mouse is very extraordinary, but the fact is now well established.... The best account which has ever been published is by an American naturalist, and I have given an abstract of his account in my Descent of Man.

"The American referred to is the Rev. S. Lockwood, author of The American Naturalist, and he gives an account of his observations of the Hesperomys cognatus, an American species, belonging to a genus distinct from that of the English mouse. This little animal gave two chief songs. Mr Lockwood gives both songs in musical notation; and adds, that though this mouse 'had no ear for time,' yet she would keep to the key of B (two flats) and strictly in the major key.... Her soft clear voice falls an octave with all the precision possible; then at the wind up it rises again into a very quick trill in C sharp and D." I have made this quotation, as it far better describes the peculiar qualifications of a singing mouse, than my inexperienced observations could announce.

'My mouse remained in contented confinement upwards of a year, feeding upon a little sopped bread and canary-seed; and great was the grief of my wife (who was his keeper) and myself when he was found dead in his little nest. During the previous evening he had been heard singing with more than usual ardour.'

We shall probably return to this interesting subject.