and the remaining 6 per cent. would be 'feeble-minded' ones. The great bulk of the feeble-minded' ones live in the bodies of normal people, and consequently the greater part of the feebleminded will continue to arise from matings between normal people, unless it should come about that more than 25 per cent. of the population were feeble-minded.

I have dwelt upon this question of the feeble-minded because it offers what the biologist regards as a typical example of the distribution of a quality in a mixed population. If we turn to what from the social standpoint is commonly regarded as a more desirable departure from the normal, viz., unusually high mental ability of some sort or another, we shall probably find that most of these at any rate are of the nature of recessive characters. Such men are very much rarer than the feeble-minded. Nevertheless the principle involved is the same. The germ-cells of the necessary factorial constitution which go to the making of such men may form but a minute fraction of 1 per cent. of the total population of germ-cells. Nevertheless the population is just as much in a state of equilibrium as in the case where the recessive appears in a much higher proportion. In a population where the supremely great intellect occurs once in 100,000,000 we may confidently look for its reappearance from time to time. For, although the individual type is so scarce, the germ-cells that are properly constituted for the quality he represents occur in individuals who, though scarce themselves, are proportionately very much more numerous. Though the outstanding individual may disappear untimely through some accident, the factors that go to his making are spread about in the germ-plasm of a number of other individuals, and these will preserve the quality for the race.

Probably there will come a time when we shall be able to apply direct chemical tests to determine whether this or that factor is present in an individual, and to decide in a few minutes whether a normal carries 'feeble-minded' germ-cells or germ-cells with factors for marked ability of one kind or another. At present we have only the cumbrous test of breeding, which, though applicable generally for animals and plants, is for man out of the question. Yet there are already some observations on record which foreshadow what is to come. We know that blood transfusion in human beings may sometimes be successful and at other times not. Recent work has shown that human bloods may be divided into four classes, and that these four classes exhibit a specific behaviour towards one another. When any two are mixed there is either a definite reaction, leading to the formation of a precipitin, or else this reaction is absent. In the latter case transfusion would be successful, though not in the former. There is evidence that these four classes depend upon the presence or absence of two

definite factors showing the usual Mendelian scheme of heredity. It is possible by the use of standard serums to take a drop of blood from a man and to decide in a few minutes what his constitution is in respect of the two factors in question. As this line of research develops (and at present it has barely started) there is little doubt that it will enable us to analyse the individual with an accuracy that is to-day beyond us.

For the biologist, then, man is a species with the various implications embodied in that word. His qualities, physical and mental, depend upon definite factors transmitted according to a definite scheme. He is polymorphic to a high degree, though probably not more so than many another beast. This polymorphism merely means that there are many factors which can be either present or absent in the constitution of the individual without affecting his humanity-factors for which we used the term 'voluntary' in contradistinction to those factors which, being present in all men, are in a sense obligatory.' It is upon the various permutations and combinations of these voluntary factors that the differences among mankind depend: upon the rarity or frequence of this or that combination will depend the rarity or frequence of this or that quality. And in so far as the factors are stable entities, so far will this stability appear in the qualities that they connote. Moreover, there is an element of stability, not only in the factors themselves, but in the proportions in which they occur in the germ-plasm of a population. When the character is recessive, even stringent measures of elimination would only produce an appreciable effect after many generations. Lamentable as this may appear in the case of the feeble-minded, the position is not without its consolations when one reflects that the majority of the qualities which we consider desirable are probably of this nature. Russia may recover from the slaughter of her professional classes more rapidly than most people imagine. Recessive characters in a population are only diminished with great difficulty owing to their enormous reserves among the impure dominants. The general character of a population is a very stable thing, highly resistant to external influences, and marked changes in its inherent nature are to be measured only in terms of centuries or tens of centuries. But it may be objected that progress is rapid, and its effects are striking in periods far shorter than the span of a man's life. To which the biologist would reply that such progress is not dependent upon any change in the constitution of the population itself, but to the appearance in it of a few individuals endowed with exceptional qualities. Those who want more progress must see to it that more of these exceptional minds are produced and given their opportunities.

R. C. PUNNETT.

THE CHARM OF THE WOODLARK

THE most recent authorities say that the woodlark is decreasing, and is not found in places where it was formerly known. But in one district of the West of England the converse is the case, for it is certainly commoner there than it was ten or twelve years ago.

When first I heard the song, one bright September morning on the way to a meet of hounds, I was quite at a loss as to the identity of the singer. But for the season, certain notes and phrases in its song would have suggested a nightingale; others resembled the desultory cadence of the tree pipit. I failed then to get a near view of the bird, and it remained a mystery to me, living, as I then was, in a county where it is unknown; twice afterwards, on visits to the West, I heard the song again, but both times under circumstances which forbade my tracking down the songster and so solving the mystery.

At last one May morning I heard once more the unknown yet familiar cadences. We were walking up a deep Devonshire lane, whose high banks were topped with beech hedges; from somewhere on our right, where fields, whose gorsey patches hinted that at no distant period they had been moorland, sloped gently upwards, the elusive, mysterious melody came, but whether from heaven or earth it was impossible to distinguish. The strain was broken, intermittent. 'Tis here! 'Tis here! 'Tis gone!' Now a few notes, faint, far off, like the tiny bells rung by heavy raindrops falling upon water; then silence; and then again, quite near, the throbbing, nightingale-like phrase. It was as though some delicate Ariel, in shape unseen, were mocking us. We stretched ourselves at length beneath the sheltering shade of a hedge and listened. And then at last the riddle answered itself. Above, almost invisible against the dazzling radiance of a May noon, the singer swam into our ken across unfathomable depths of blue sky. The bird could only be a woodlark; the difference between his wide, irregular circles and the spirals of the skylark was obvious. Like his cousin, 'a privacy of glorious light' was his; even when we saw him our uplifted eyes were momentarily almost blinded. In broad ellipses he made his winged ascent into the empyrean, then glided downwards, and then, with a few swift

wing beats, rose again. Both song and flight were wayward, impulsive; he was 'Nature's child, warbling his native woodnotes wild.' A sudden dive to earth ended our Ariel's melody. Carefully we stalked him and found him quite tame and not averse from our making his closer acquaintance. We could mark his short tail, pale yellow eye-stripe, continued round the back of the head, his almost black crest, the small black-and-white mark on the shoulder ' of the wing, and his pretty pink legs and feet. His identity was clearly established.

Since then I have had many opportunities of becoming familiar with this delightful bird, for I now live in a district where woodlarks are common. They seem to prefer low-lying country, and are rarely seen on open moorland, though both in and out of the breeding season I have come across them in rough pasture bordering the moors at an altitude of 1000 to 1200 feet. For months they haunted the land round my house, and at length, to my great joy, a pair built a nest in rough grass not many yards from the edge of my lawn.

The lovely song deserves more detailed comment. Both in quality, as well as in the actual notes, it is entirely distinct from that of the skylark, who pours out his

The woodlark's vers libres are more meditative, as though he paused betweenwhiles to take pleasure himself in their beauty. Were his song not so artless, one might hazard the guess that he had studied the technique of metrical pauses to some purpose. The same difference in mood is apparent in the songs of blackbird and thrush; the throstle, like the skylark, has the robustious exuberance of a prima donna; both merle and woodlark are, to my mind, truer artists, because they exercise more restraint.

The woodlark's song may be heard in any month of the year, except, perhaps, in August. Last year they went up with a merry noise all through the dismally wet autumn and winter whenever the sun came out in the morning. One bright, warm day in January they sang perpetually, almost without a pause. Perhaps the music reaches its highest perfection in April and early May. At this time, singing as often as not from tree or post, the woodlark's flow of melody may be for a short period almost as continuous as the skylark's' silver chain,' though always more varied. The finest passage is the trill, descending chromatically with infinitely small gradations, which recalls to mind a well-known phrase in the nightingale's song; there are, indeed, in the woodlark's, delicate nuances of tone-colour, of piano and forte, which are not, so far as I am aware, attained by any other British songster except

Philomela. These piano phrases occur even when the bird is singing from a perch, and thus cannot be due to its nearness to, or remoteness from, the listener. While singing, the woodlark turns his head from side to side, but for a bar or two he will sometimes drop his voice; it is this trick which imparts the contemplative character to certain passages, as though he were singing to himself. And then, again, the sudden silences heighten the listener's expectation. When he is singing in the air these unconscious, innocent ruses clothe the song with that faërie elusiveness which is so well expressed in the late Father Hopkins' littleknown poem:

So tiny a trickle of song strain ;

And all round not to be found

For brier, bough, furrow or green ground

Before or behind or far or at hand

Either left either right

Anywhere in the sunlight.

He will go on to execute a series of shakes, first on one note and then on another a little higher; this will be followed by a single note often repeated; in fact, he improvises on notes pitched now high, now low, in a scale whose infinitesimal modulations are imperceptible even to the musically trained human ear. I have heard the song at night, at dawn, and at dusk; when snow lies thick upon the ground he will still sing, if the sun comes out, or in warm rain when it is cloudy. He will soar into a strong wind, progressing by means of little leaps upward with half-folded wings, and still pour out trills of gusty melody.

Courtship, with its attendant combats, begins early in the year. Owing to the similarity in the appearance of male and female, it is difficult to distinguish the sexes. True, the hen is said by one authority to be 'usually smaller, duller in plumage, more flecked, and shorter in the wing.' But it is practically impossible to note these distinctions in the field. At first I thought that I could see a slight difference in the colour of the pair which I had under close observation during last summer, but I was eventually driven to the conclusion that there was no real dissimilarity. In some lights the cock looked paler than the hen; in others the reverse was the case; in size they appeared practically the same. This similarity sometimes made it extremely difficult to decide whether a particular piece of behaviour was referable to courtship or to a preliminary contest between two males. In mid-January last year there was a small party of eight woodlarks on my land. One, evidently a cock, sang from a perch in the hedge, and also gave the call-note (usually written 'too-lui-ie '), to which one of the others responded with two soft notes, 'wee-ou,' the first slightly higher than the other. I have no doubt that the answering