The lower vertebrates never develop these cortical tracts, and just so surely their vision remains of a primary character. A hungry snake will crawl over a mouse without noticing it, provided the "tim'rous beastie" keeps still. It will swallow a dead mouse if the latter is kept in motion. But in the birds, where the primary optic centers first acquire connexions with the cortex, we find an entire change of mental power. Many experiments and observations show that the feathered world understands what it sees and associates therewith its earlier sight impressions.

It should not be overlooked that with the evolution of the cortex proper there is found a parallel increase of associative mechanism. As Professor Edinger states it, "Nothing characterises the mammalian brain more than the development of numerous and massive association tracts along with increase of the cortex." And here again mental evolution goes hand in hand with that of anatomical structure. Sense and substance, faculty and fabric, mind and matter are parallel and inseparable.

It will therefore be seen that the great authority of Professor Edinger is thrown with those who believe that differences in mental endowment imply differences in cerebral structure. In regard to what these differences are and in regard to the localisation of psychological functions in the cortex, he acknowledges the meagerness of present knowledge, admits the inadequacy of methods hitherto employed and shows clearly how the anatomical difference essential to a great quality of mind might exist in a given brain without its being perceptibly altered from the average in weight, shape, or convolutions. On this point he cites strong evidence and suggests interesting lines for investigation.

He further expresses the belief that the brain is a progressive development; that "no boundaries can be drawn between the mental possessions of the lowest and the highest vertebrates;" and finally that the evolution of the human brain and human intellect has not yet reached its maximum. E. P. LYON.

KULTUR UND SCHULE. Präliminarien zu einem Schulfrieden im Anschluss an die Preussische Neuordnung von 1 April 1892. Von Dr. Alex. Wernicke, Osterwieck: A. W, Zickfeldt. 1896. Price, M. 2.40.

The pamphlet is a protest against the narrowness of those educators who would give all advantages to the gymnasial course and deprive the Realschulen even of the privileges which have reluctantly been conceded to them in Germany. The author is a man of serious convictions fighting for a noble cause. A discussion of his expositions would be out of place here, because whatever the school problems may be with which we are confronted in English-speaking countries, there is little danger of tyranny on the part of classical philologists.

ADAM SMITH'S PÄDAGOGISCHE THEORIEN IM RAHMEN SEINES SYSTEMS DER PRAKtischen Philosophie. Von Dr. phil. Paul Bergemann. Wiesbaden : Emil Behrend. 1896. Pages, 64. Price, M. 1.20.

Adam Smith's theories of political economy are well known while his views on the subject of education are neither remembered nor recognised. Dr. Bergemann therefore calls attention to Adam Smith's pedagogical propositions, which are treated in several chapters of his Inquiry Into the Nature and Causes of the Wealth of Nations, and sheds light upon their significance by setting them forth in their historical connexion and contrasting them with the views of other contemporary thinkers.

The editors of the Vierteljahrsschrift für wissenschaftliche Philosophie propose a prize of five hundred marks for the best solution of the following problem: "Nachweis der metaphysisch-animistischen Elemente in dem Satz von der Erhaltung der Energie und Vorschlag zur Ausschaltung dieser Elemente."

The essay must be written in German, but competition is not limited to any nationality. Size should not exceed fifty or sixty pages of said magazine. Latest term, October 1. Address the editors of the Vierteljahrsschrift, Privatdozent Dr Fr. Carstanjen, Zürich V Englisch Viertel 49, or Dr. O. Krebs, Zürich V Minervastrasse 46.

Instead of the author's name each essay is to be superscribed by a motto. An accompanying envelope, also superscribed by the motto, is to contain the author's real name and address. The judges will be: Prof. Dr. Ernst Mach, of Vienna Prof. Dr. Alois Riehl, of Kiel, and the two editors of the Vierteljahrsschrift.

Mr. Thomas J. McCormack, the translator of Prof. Ernst Mach's Mechanics and Scientific Lectures, and of numerous other scientific works offering great difficulties to reproduction in English form, has been connected with The Open Court Publishing Co. since the foundation of The Monist and has rendered the editor much valuable assistance both in the reviewing of books and in the general supervision of the editorial work. Beginning with the April number he will be more closely associated with the staff of both The Monist and The Open Court in the capacity of assistant editor.

THE MONIST.

ON EGG-STRUCTURE AND THE HEREDITY OF INSTINCTS.

THE

HE INSTINCTIVE ACTIONS of animals are hereditary and can only be transmitted through the sexual cells. The problem of heredity from the physiological standpoint is, in brief, as follows: How can an egg, a simple vesicle filled with a viscous liquid which contains some solid constituents, be the bearer of such complicated mechanisms as the hereditary instincts? Two views are possible a priori: either the simplicity and homogeneity of the egg is only an illusion, and in reality it contains an invisible mysterious structure, of a similar degree of complexity to the adult animal; or the complicated mechanism of the instincts is the result of very simple circumstances which do not require any complicated structure for their transmission through the egg. All other possible suppositions are only compromises between these two possibilities. We shall here briefly present an argument in favor of the latter solution, which, we hope, will do away with some of the mystic aspects of heredity, and render a number of very complicated, albeit ingenious, theories redundant.

I.

The first view, which has been of late very ably expounded to the readers of The Monist, is held, among others, by Nägeli and Weismann; not so much, however, for the sake of accounting for

the heredity of instincts as for the explanation of the continuity of forms in general. As the mysterious egg-structure which this theory presupposes is admittedly invisible, it is impossible to prove directly its non-existence. To the second view we are necessarily led when we attempt to analyse the instincts into their elements, which will deprive them of much that seemed very mysterious before. A few salient examples will be sufficient to throw a new light on the subject.

1. The larvæ of a certain butterfly (Porthesia chrysorrhea) hatch in Germany in the fall and hibernate in large numbers in a web on trees and shrubs. The warm spring sun drives the larvæ out of their nest, and they creep upward on the branches of the tree until they reach the highest points, where they find in the young buds their first food. As soon as they have eaten, they creep down on the branches until they find new buds or leaves which in the meantime have appeared in abundance. It is apparent that the instinct of the caterpillars to creep upwards after they awake from their winter sleep saves their lives. If they were not guided by such an instinct, those that crept downwards would perish from lack of food. How can such an instinct be transmitted by a single cell?

Experiments which I made eight years ago prove that the young caterpillars of Porthesia, as long as they are starving, are oriented by the light, i. e., the light causes them to bring their plane of symmetry into the direction of the rays of light, and to turn their oral pole toward the source of light. This process is purely mechanical. The light produces in the skin of the animal a change (probably chemical), and this produces, through the central nervous system, changes in the tension of certain muscles. Suppose the light falls upon the right side of the animal. This would lead to an increase in the tension of the muscles which turn the head and body of the animal to the right. As soon as the head of the animal is turned towards the source of light and its median plane is in the direction of the rays, the symmetrical points of the surface are cut by the rays of light at the same angle, and the chemical effect of the light is the same in each pair of symmetrical points of the surface of the animal. Correspond

ingly, the symmetrical muscles of both sides of the body are under equal tension, and there is no reason why the animal should deviate more towards one side than towards the other from the direction of the rays of light. Thus the animal goes towards the source of light. I may mention here, by the way, that this is also the mechanism by which the moth is forced into the flame. There is no such thing as an attraction of the moth by the light, but its fatal flight is only due to an orientation. We call those animals that are forced to turn their heads towards the source of light, and that consequently go towards the source of light, positively heliotropic.

Positive heliotropism of the young caterpillars of Porthesia leads them to the tips of the branches where they find their food. During the cold of winter they are rigid and immovable, the higher temperature of spring produces chemical changes in their bodies which causes them to move. The direction of motion, however, is dictated by the light. In the open air, where the light of the sky falls from all sides upon the animals, we may decompose each ray of light into a horizontal and vertical component. The horizontal components annihilate each other, and only the effect of the vertical component will remain. The animal, therefore, on account of its positive heliotropism, must creep upwards until it reaches the tip of a branch. Here it is held by the light. The chemical stimuli which are given to the animal by the young buds, determine, in a machine-like way, the feeding motions.

From these data we are able to answer the question, how much of a structure must be contained in the egg of Porthesia, in order to render possible the heredity of this curious instinct of the young caterpillars? The answer is, the egg must contain, first, a substance which is sensitive to light. This is possible without any complicated structure, even if we assume that the egg is only a mixture of different unformed substances. But this is only one of

the elements which determine the positive heliotropism. The second circumstance is, as we have seen, the bilateral symmetry of the animal. For the transmission of the instinct, this, too, must be determined by the egg. This makes it necessary that a differ

ence of the ventral and dorsal, of the oral and aboral pole is already