never metamorphose at all, never even form legs, but continue to grow and grow into giant tadpoles double and treble the size of any found in nature. Some of these have finally been found to become sexually mature; and it is hoped in the near future that young may be obtained from them.

Now there exists in Mexico and the Southern United States a remarkable creature known as the Axolotl (which, by the way, is Mexican for 'play-inthe-water'; it may be added that the Mexicans eat them in quantities, stewed or fried, with plenty of cayenne pepper). This creature looks like an aquatic salamander, and lives in lakes and pools, where it breathes by gills. It closely resembles the enlarged tadpole of a newt, which differs from that of a frog in early possessing legs. Another animal of about the same size is known, from the same regions, the Amblystoma. This lives on land, and is definitely a large salamander, air-breathing and finless.

In the middle of last century it was discovered that these two apparently very distinct animals were really one and the same, and that the amblystoma always started life as a little axolotl, undergoing metamorphosis later. In certain districts, however, the change never came, and the axolotls simply continued to grow and finally to become capable of reproduction in their tadpole state.

Now by means of a thyroid diet, any axolotl, no matter how large or how mature, can be turned into an amblystoma a transformation involving not only the disappearance of gills and tail-fin and the growth of lungs, but also an extra growth of limbs, a change of color, and extensive alterations in the skull and skeleton.

But the last link in the chain remains. There are three or four other species of animals in America which closely re

semble the axolotl, spending their piscine existence in ponds and streams, but which are not known in a land-form at all. Apparently they have found aquatic existence to pay better, and in them the thyroid seems to be so reduced that they can normally never metamorphose. Biologists in the United States are now endeavoring to get hold of some of the young of these, and to see if thyroid-feeding will induce them, too, to change to a terrestrial creature. If so, it will be to a form which has been lost for thousands or tens of thousands of years, and science will have resuscitated a type of life which, without her, would have been forever extinct.

These results are interesting enough. in themselves, but the question remains, how the thyroid accomplishes what it does. On this point, no certainty has been reached. The view I have come to may be indicated because of its bearing upon other questions. Briefly, it is this. In a developing frog the processes of growth first built up a system which we call the tadpole. Development continues, and leads, partly to the growth of this tadpole-system, but partly to the building up of a new system, the rudiments of the frog. These consist chiefly of the beginnings of lungs and limbs; but many changes in the skeleton, too, are initiated, which have meaning only when looked on as forerunners of the adult state.

After a time, then, we have two systems of organs competing with each other within the single organism - the formed tadpole-system, and the forming frog-system. The action of the thyroid is, I believe, to stimulate the young, growing frog-tissues more than the older, differentiated tadpole-tissues; or, even more probably, to over-stimulate the tadpole-tissues, and so give the frog-tissues more of a chance. When the thyroid has produced enough of its

secretion, or when enough is introduced in the diet, the growth of the frog-system is so much accelerated that it beats the tadpole-system in the competition for food. The tadpole-tissues are in these conditions unable to maintain themselves, they break down, and become utilized as food-stuff by the remainder of the organism.

The underlying processes of life have often and justly been compared to an eddying stream; and this comparison will help us to visualize such a process. The structure of the organism can be represented by the bed of the stream; its vital processes by the flowing water. Alter one, and you alter the other. Imagine a stream flowing round an S-shaped bend, and in the first curve swirling under the bank in a broad eddy. If a little channel is dug across, so as to short-circuit the second bend of the S, water will flow along this, and less will be left for the eddy. Anything which enlarges the channel will increase the flow along it, and as this increases, the eddy will lose its original character, and finally the whole of the second bend will dry up and cease to be. If the eddy in the bend represents the life animating the tadpole-system, the stream along the new cut that of the growing tissues of the adult, then, if we have a workman with a spade coming and enlarging the new channel, he will represent the thyroid. That such struggling systems are not mere convenient imaginations chosen to suit the case is shown by numerous examples, two of which may be cited.

Clavellina, the Ascidian that we have already studied, belongs to a group of animals which, though degenerate in that they live a sedentary life, are yet of a high order of complexity, and, as a matter of fact, are degenerate offshoots of the ancestral vertebrate stock. Another of these, called Perophora, grows in a very plant-like way, sending out

hollow shoots, full of circulating blood, from which at intervals new buds arise, so that a colony of individuals is produced with a common blood-system.

By snipping this shoot, or stolon, at two places, we isolate a system consisting of a single individual and a piece of stolon. In the laboratory it is impossible to provide the creature with the minute floating food which it finds in the sea. In spite of this, such systems, if kept in pure water, live under observation for a long time. If the water is constantly renewed, the individual continues healthy, and of the same size; but the stolon progressively shrinks, because its tissues are being used up to provide nourishment for the more highly organized individual, which in these conditions is the dominant partner.

If, on the other hand, the system is placed in extremely dilute solutions of various poisons, we can achieve a curious result. At a certain concentration, of course, the whole system is killed. At a lesser concentration, both individual and stolon are badly affected; but a still greater dilution can be found, in which the more highly organized and therefore more sensitive individual is considerably affected, the simple stolon scarcely at all. In this case the individual shrinks, it loses its typical shape and becomes an irregular sphere, its organs collapse and become simplified, as if it were about to de-differentiate; but after a time the separate cells actually migrate out of the tissues into the blood-stream (as if a house were to unbuild itself by the bricks flying out of the walls!), and finally nothing of it is left. The stolon, meanwhile, not only keeps healthy, but may actually continue to grow at the expense of all the food-material thus provided. In fact, the boot is now on the other leg the dominance is reversed. The system thus consists very clearly

of two lesser systems in competition with each other. When both are healthy the most active and highly organized wins; but this is more sensitive to unfavorable conditions, and, once it is affected, is unable to keep up the struggle, and is actually sucked out of existence by the other,

Growth and the reverse of growth, seen in the sudden disappearance of whole systems of organs, may thus in certain cases depend on the upsetting of a balance between contending parts of an organism.

To complete our survey, we might take one further example from a very different field that of the mind. It is well known to those who have studied nerve-disease that one set of symptoms that occurs regularly in a certain proportion of patients suffering from shell-shock and neurasthenia can be classified as mental regression-in other words, a going backwards to an earlier stage of mental life. Grown men behave like boys of five, lisp, forget their adult life, talk as if the memories of that early time alone were active in them, play childish games, become dependent on their nurses. In fact, they become, as nearly as their grown body permits, what they were, or what they remember to have been, at some farpast age. When this condition is carefully analyzed, it is found that it, too, is the result of a competiton between two systems of mind

the adult sys

tem and that of earlier times, when life was remembered as happier.

In times of severe strain, to keep the adult system going involves a constant facing and overcoming of unpleasant fact. Under these conditions, its delicate adjustments are upset, its nerves become exhausted, the nervous energy will no longer flow so readily through its channels. But nervous energy is continually welling up as a product of the activities of life; and so, being re

fused its proper channel, it runs into that which it finds most open to it. In some, this second channel is an imaginary world; in others, it is the channel that leads to despondency and suicide; in still others, it is, as we have seen, the simple revivifying of the old and less complex systems of childhood.

We seem to have wandered far afield; and yet this idea of lesser systems in competition within a greater is one of extreme importance for our problem. In the sequel, we shall see to what conclusions it leads us.

The administration of pituitary substance to the single-celled Paramecium led, as we saw, to increase of growth and reproduction. It has been established, too, that it encourages the growth of cancerous tumors in mice. But the results of feeding young growing animals with it have all led to a puzzling and apparently contradictory result growth is not accelerated, but retarded. Later, however, it was discovered that this stunting is only temporary, and is followed by a later increase of growth, the final size of the animal being sometimes above the normal. This has been shown to hold good for the pituitary itself, and especially for an active substance, christened tethelin, or the growth-promoter, which Brailsford Robertson has succeeded in isolating from the pituitary.

What is more, it was found that a continued administration of tethelin not only affected growth in this way, but actually lengthened the life of the animals receiving it. The average life of Robertson's normal mice in captivity was about two years 767 days, to be precise. The average length of life for tethelin-treated mice was 100 days longer. Their life had been lengthened by over 12 per cent.

These last findings lead us naturally on to consider the duration of life and its possible prolongation. But before

turning to this particular problem, I would like to bring up one other, not only because it so well illustrates the suggestiveness of our knowledge, but because it also reveals how great are the uncharted tracts of our ignorance.

cer

The problem I refer to is that of can

cancer, which kills one woman out of every nine, one man of every thirteen; to whose perennial ravages those of the greatest wars are nothing. Of the ultimate cause of cancer we know next to nothing. It is probable that there are many such causes. Sometimes it appears to be due to local irritation, sometimes to a poison, sometimes, again, to some ultra-microscopic germ. But the end-result is always the same: some of the cells of the body become, through this or that agency, emancipated from the controlling bond which regulates the growth and harmony of the parts in the whole, and the emancipated tissue embarks upon a career of unlimited, unregulated growth and reproduction.

Let us for a moment revert to the question of growth in man or the higher animals. It should be emphasized once more, how the power of growth inherent in the germ, at first enormous, decreases continuously as development proceeds.

This may be illustrated by a very simple calculation. The weight of the human germ or ovum is about six tenths of a milligramme. The weight of a new-born baby is from three to four kilogrammes. Thus, in the nine antenatal months the ovum increases its weight five or six million times. In the remaining eighteen or twenty years of active growth, however, the child increases its weight only fifteen to twenty times.

power of budding, and regenerating lost parts, so often seen among the lower animals, is present in the young stages of the higher types, but not in the full-grown individuals. If one chooses to take a Planarian flatworm and simply cut it into bits, most of them will grow new heads and tails and become flatworms again, perfectly healthy though small. This is not possible in a newt, although even here amputated legs are produced afresh. In a lizard, a new tail can still be grown, but not limbs; while in a bird or a mammal, no large part can be regenerated; a limited regeneration still takes place, however, to the extent of healing over cut surfaces.

But if, even in these higher types, we go back to the early stages of development, we find a much higher power of regeneration (and regeneration is of course bound up with the power of growth). A frog cannot replace an amputated limb. A tadpole can, and does with ease. Even in mammals this power is retained. Some ten years back, the zoological world was startled by the discovery of a Texan naturalist that the common armadillo of the southern United States reproduces partly by budding. Four young are always produced in a brood, and these all arise from a single original germ, which buds out the four rudiments of the future young armadillos after reaching the three-layered stage. In man himself there is no reasonable doubt that what we call identical twins - twins so nearly alike that confusion is possible between them - arise in a similar way by some form of budding from a single ovum; and that this common origin is the cause of their extraordinary resem

THE Conquering Entente is still at work in Austria. After the division, under the Versailles Treaty, of the old Austro-Hungarian Empire into a number of small nationalist states, the small state of German Austria has been left economically crippled and politically crushed; because German Austria is an industrial territory, which formerly drew its raw materials, coal, and food from Hungary and other provinces, furnishing them in turn with manufactured articles. Now these new states have adopted all the vices of petty capitalistic nationalism, with rigid tariff restrictions, with national hatred, with political and military ambitions copied from their friends and masters, the Entente. They refuse to sell food to Austria, they refuse coal for Austrian factories, and they still live upon memories of the injuries which they-and Austrians as well-suffered royalty.

under

As in Germany, the Entente pursues two obvious lines of activity in Austria. One is to 'destroy militarism' by taking all Austrian war-material for their own use; and the other is to prevent the country from adopting Communism and thereby abandoning the civilization of the Entente. In Austria, in order to realize this latter desire, the Entente finds itself face to face with the necessity

of furnishing the necessary capitalistic props.

Two of the large Entente commissions the Reparations Commission here now, and the Interallied Military Control Commission, which left on February 20― are the most outstanding examples of Entente activity and morality in Central Europe. The commissions came as conquerors; they came with all the hatred that conquerors feel toward a proud people who have resisted their onslaughts until starvation alone forced them to surrender. They came with hatred for the nations which for centuries have produced, conscious of their greatness, most that Europe has of inspired music and philosophy, and much of its great literature and art. The conquered nations do not admit a greater guilt than that of the Entente. And it is because they do not, and will not, that exactions are all the more rigid.

The expenses of the Entente commissions in Austria are paid by the Austrian state, which is admittedly bankrupt. When the Interallied Military Control Commission withdrew on February 20, after ten months of occupation, it had spent from Austrian state funds the modest sum of 710,050,000 kronen, a staggering sum for Austria. It then left behind a ‘Liquidation