tion of his hypothesis of inheritance. Its extreme elaboration is its greatest weakness, and in it, no less than in all preceding hypotheses, the theory of a separate category of particles carrying hereditary potentialities again appears.

The one criticism that holds of all these hypotheses is that they are one-sided and ignore a most important set of factors in inheritance, namely, the purely statical ones, or those arising from the mere physical properties of the living matter of the germ viewed as if it were a dead, inert mass, subject to the operation of the reciprocal attraction for one another of its constituent particles. All of these hypotheses, moreover, assume that it is only some of the matter of the germ that is concerned in the process of hereditary transmission, and that the remainder may be regarded as passive. The entire germ, on the contrary, or all of it that undergoes development, must be considered as a single whole, made up of a vast number of molecules built up into a mechanism. Such a molecular mechanism, it must be supposed, cannot set free the potential energy of its parts except in a certain determinate order and way, within certain limits, in virtue of the initial physical structure of the whole. If the germ is free to do that, as must happen under proper conditions, as a mechanism, its parts, as they are thus formed by their own metabolism, it may be assumed, will inevitably and nearly recapitulate the ancestral development or that typical of the species. It must do this as a mere dynamical system or mechanism, the condition of which at one phase determines that of the next, and so on, to the completion of development.

In the present state of our knowledge we are not prepared to frame a purely mechanical hypothesis of inheritance that shall answer every requirement, in spite of the fact that no other is possible. Herbert Spencer and Professor Haeckel long ago pointed out

that such an hypothesis is a necessity growing out of the very requirements that must be satisfied in any attempt to coördinate the phenomena of biology with those of the not-living world. The material basis of life is always a chemically and mechanically compounded substance. To the very last molecule, such a body must betray evidence of arrangement or structure of its parts that should make it a mechanism of the utmost complexity and requisite potentiality as a transformer of energy through the mere transposition and rearrangement of such parts. We find indeed that living matter is chemically the most complex and unstable substance known. It is composed largely of carbon, a quadrivalent element that stands alone in its power to combine with itself and at the same time hold in chemical bondage groups of atoms representing other chemical bodies. Such groups are probably held together in great numbers metamerically by the reciprocal or otherwise unsatisfied affinities of the large number of carbon atoms entering into the composition of the proteid molecule. In this way the massive and structurally complex molecule of protoplasm may be supposed to have arisen. We may thus trace the genesis of the peculiarities of living matter to this singular property of the carbon atom. On such a basis we may suppose that the ultimate molecular units are identical with the physiological units, so that their structures may not only determine the nature of the metabolism they can undergo, but also be the ultimate units of form or morphological character.

What especially gives color to these suspicions is the extraordinary variety of changes, alteration of properties or powers, and the vast variety of living matter, as represented by the million or more of known distinct living species of organisms. It is as if the permutations, transformations, and the dynamical readjustment of the meta

meres of the molecules of living matter were the source of its varying potentialities as manifested in its protean changes of specific form and function. That some mechanical and consequently dynamical interpretation of these transformations may yet be forthcoming is, I take it, distinctly foreshadowed by the advances in the newer theories of stereo-chemistry developed by LeBel and Van't Hoff. If this is the case we may yet hope for a mechanical and dynamical explanation of the phenomena of life and inheritance. Especially is this true if we further suppose that the large molecules of living plasma are rather feebly held together by a force almost of the nature of cohesion. We may be permitted thus to find an explanation of that phenomenon which is always so characteristic of living matter, namely, the large and relatively fixed amount of water it contains, and also the mobility of its molecules in respect to one another, its jelly-like character at one instant, its fluidity and power of motion at another. It is indeed probable that the amount of water contained in living matter is controlled within certain limits by the forces of cohesion exerted between adjacent molecules against the osmotic pressure or capillary action of water tending to drive them asunder, as supposed by Nägeli, in his hypothesis of micellæ. Such an hypothesis enables us to explain much that is otherwise quite unintelligible in relation to living things. It renders us an explanation of amoeboid motion, of the surface tensions of protoplasm and lastly of metabolism itself through osmosis and the specific characters of the chemical transformations that must take place in each kind of living substance.

Such an hypothesis may also afford us mechanical constructions of atoms, grouped into very large metameric or polymeric molecules of the utmost diversity of powers, capable of undergoing a long series of suc

cessive transformations, so as to manifest in the long run, starting with a molecular germinal aggregate, what we call ontogeny or development. These transformations, we must suppose, are effected by the metabolism incident to growth, and moreover, that starting with an initial configuration of a system of molecules, as a mechanical and consequently a dynamical system of determinate powers, in the form of a germ, it cannot undergo any other transformations except such as lead to an approximate recapitulation of the ancestral development or phylogeny. This supposition follows from the rule that must hold of determinate systems of molecules, as well as of systems formed of larger masses, namely, that the initial changes in the configuration of such a complex system must dynamically determine within certain variable limits, under changing conditions, the nature of all of its subsequent transformations, including those due to growth and consequently increased complexity. We thus escape the necessity of invoking certain 'proclivities' of physiological units, or the necessity of appealing to the growth and fission of 'biophors' or the scattering of determinants' at the proper times and places in the course of development. We thus escape, too, the mistake of assuming that a part of a germ controls the whole, a proposition that has been so long advocated by one school of biologists that it is astounding that its fallacy has not long since been more generally understood. Such a doctrine is not credible in the face of the fact that we know of no development except that which takes place in intimate association with cytoplasm, which seems to be the principal theater of metabolism and growth. We cannot conceive of the transformations of a germ without considering the metabolism of all its parts, such as nucleus, cytoplasm, centrosomes, archoplasm, chromatin, spindles, astral figures, microsomata, etc.

'Tendencies' and 'proclivities' are words that have no legitimate place in the discussion of the data of biology any more than they have in natural philosophy or physics. Karyokinesis, now admittedly inseparable in thought from the idea of multicellular development, is a rhythmical process so complex in its dynamical aspects as to some extent lead one unwittingly to underesti mate the absolute continuity of the accompanying processes of metabolism. But that is no reason why the importance of nuclear metamorphosis should be exaggerated at the expense of the far more important forces developed by metabolism and growth. In fact, the 'ids,' 'idants,' etc., of that school of biologists are not causes but mere effects, produced as passing shadows, so to speak, in the operation of the perfectly continuous processes of metabolism incident to development. Reciprocal relations are sustained between nucleus and cytoplasm of such importance that the transformation or fission of the one is impossible without the other.

The so-called 'reducing divisions' probably have nothing but a passing and purely adaptive physiological significance in every ontogeny of ova and sperms. The far-fetched and extraordinary teleological significance given by some to the reducing divisions would lead one to suppose that the clairvoyant wisdom of the original egg that thus first threw out the excess of its ancestral 'germ-plasm' in order to save its posterity from harm through the fatality of reversion thus entailed was greater than anything human, if not god-like. The complete parallelism of the 'reducing division' in the sperm and egg has never been established. The comparison of these processes in the two is still only approximate, because in the truly holoblastic egg there is, in some cases, an apparent temporary substitution of the male nucleus for the female, as is shown by the former's assuming a position

of equilibrium at the center of the ovum (Ascaris), a condition of things that does not and could not occur in the sperm cell.

A still more important contrast is the almost incredible difference of volume of the two kinds of sex-cells of the same species. In man the ratio of volume of the male cell to the female cell is as 1 to 3,000 approximately. This extreme contrast of volume is associated with corresponding contrasts in their properties. There can hardly be any doubt that the mature male cell is in a nearly potential or static state of metabolic transformation of its substance, and is characterized by an almost complete want of stored metabolizable reserve material. The egg is in a similar static state, but, on the other hand, contrasts with the male element in that the development of a more or less voluminous mass of reserve material within it has seemingly been also associated with its loss, as a rule, of the power to begin an independent development. The power of the male cell to begin its transformation and growth through metabolism appears to be arrested until it finds the material in which its mere presence will set up transformations. This it must do by in some way ting free and diffusing some of its own molecules osmotically and mechanically through the egg. The substance of the egg appears therefore to be complementary to that of the spermatozoön. The power to set up transformations within the egg leading to the development of a new being is not manifested aside from the presence of the male element except in cases of parthenogenesis. Even the expulsion of the polar cells is not initiated until the stimulus of the presence of the male element is experienced by the egg.

set

Another contrast is found in the times of the advent of the 'reducing division' in the two kinds of sex-cells. In the male cell the reducing division' occurs earliest, or while it is still in more or less close nutri

tive relation to the parent; in the egg the 'reducing division' or expulsion of polar cells does not occur till the egg is freed, as a rule, from the parent gonad, and generally as a consequence of the stimulating effect of the presence of the male cell. These differences of behavior of the two sorts of sexcells seem to be correlated with their dif ferences in size.

We may contemplate the sex-cells as molecular mechanisms which, in virtue of their mechanical structure, are rendered capable of controlling the order and manner of rearrangement of their constituent molecules, because of the new successive attractions and repulsions set free, amongst the latter, immediately upon the completion of conjugation. The new forms of metabolism thus initiated enable us to conceive a mechanical theory of fertilization. At any rate, the two sorts of sex-cells are potentially the reciprocals of each other, and their initial or statical states cannot begin to set free their energy and thus pass into the successive kinetic states of formal change until the two mechanisms are reciprocally and mechanically integrated into a single one by means of conjugation. The parts of this new single body now act in unison. Even the manner in which the two conjoined molecular mechanisms operate can actually be to some extent traced, as expressed in the complex movements associated with fertilization, the division of the chromosomes and centrosomes. The effect of conjugation is to afford opportunity also for new and various combinations of molecular mechanisms, though the reciprocal integration of pairs of cells having a widely different parentage.

The great size of the egg-cell provides an extensive reserve material that enables the embryo thus built up usually to reach a relatively great size without entering for a time into competition for food in the struggle for existence. Sexuality is therefore

altruistic in nature, since it has led in both plants and animals to the evolution of a condition of endowment, or the storage of potential energy in the germ, so that the latter is the better able to cope with natural conditions. While it may be assumed that sexuality has arisen, in the main, under conditions determined by natural selection, once sexuality was attained, the added power thus accumulated potentially in large germs of double origin enabled the latter the more easily to overcome untoward natural conditions. Natural selection thus becomes altruistic or dotational in that it tends through sexuality to defeat the deadliness of the struggle for existence, just as we may also assert that the theory of superposition to which the mechanical theory of development is committed is also finally altruistic. altruistic. It may be remarked that the greatest mortality of a species, under the conditions of the struggle for existence, also takes place in the egg and embryonic stages, or before organisms can experience acute pain; so that here again we have a result that must materially ameliorate the pains and penalties of the struggle for life.

These details are, however, of minor import for us just now. The important thing to bear in mind is that all of the forces of development are ultimately metabolic in origin, and that the wonderful order and sequence of events in any given ontogeny arise from the transformation or transposition of the parts of a molecular system that also thus increases in bulk by the addition of new matter. The steps of this transformation are mechanically conditioned by dynamical laws with as much unerring certainty of sequence as those that control the motions of the heavenly bodies. The consequence of such a view is that we can thus free our minds of all traces of belief in a theory of preformation. The embryo is not and cannot be preformed in the germ, as

observation and physiological tests prove; nor is such preformation necessary if a mechanical hypothesis is adopted.

JOHN A. RYDER.

(To be concluded.)

CURRENT NOTES ON PHYSIOGRAPHY (VIII.) CROWLEY'S RIDGE.

CROWLEY'S RIDGE, rising above the alluvial lowland of the Mississippi in Missouri and Arkansas, has long been a subject of discussion. Branner (Geol. Surv. Ark., Ann. Rep., 1889, ii., p. xiv.) has suggested that the lowland to the west of the ridge was excavated as an early path of the Mississippi, from which it was diverted into its present course east of the ridge by the Ohio; but it is difficult to understand how the smaller of the two rivers could divert the larger one. A new explanation of the ridge has recently been offered by C. F. Marbut (Proc. Boston Soc. Nat. Hist. xxvi., 1895), to the effect that the ridge is homologous with the Chunnenugga ridge of Alabama, and that it belongs to a family of geographical forms frequently found on coastal plains during the mature stages of their development. These ridges or uplands normally run parallel to the coast line; they mark the outcrops of comparatively resistant strata, dipping toward the coast; they descend inland by a relatively rapid slope, often strong enough to be called an escarpment, towards an inner lowland which has been eroded on an underlying and weaker member of the coastal formations; they descend more gently on the coastal side. The inner lowland is drained by longitudinal streams, which enter transverse streams that cut their way through the ridge or upland on the way to the sea. In a region of uniform uplift all these features of relief and drainage have a regular rectangular system of trends; but where the former shore line or the uplift is irregular the trends will depart more or

less from a rectangular towards a curved pattern. Marbut regards Crowley's ridge as a portion of an inland-curving ridge of this kind. The master stream of the region is the Mississippi, which bisects the inland curvature of the ridge. The upland along whose eastern base the Tennessee river flows northward in an adjusted subsequent course forms the eastern part of the curve; while Crowley's ridge forms the western part. The lignitic strata by which the ridge is determined weaken southwestward, and hence the ridge soon disappears in that direction. The lowland west of Crowley's ridge, ascribed by other writers to erosion by the Mississippi, is explained by Marbut as comparable to the lowland on the inland side of the Chunnenugga ridge of Alabama, and the rivers which follow this lowland are thought to be adjusted subsequent rivers.

THE CUSPATE CAPES OF THE CAROLINA COAST.

THE systematic repetition of certain features in Capes Hatteras, Lookout and Fear is explained by C. Abbe, Jr. (Proc. Boston Soc. Nat. Hist., xxvi., 1895) as the result of a number of backset eddying currents, turning from right to left between the Gulf Stream and the coast. The generally southward movment of the sands along the shore being well known, some special explanation is needed for the acutely pointed capes between the smooth concave curves of the sand bars. Although this is a conspicuous feature of the coast, it seems to have been little considered. Shaler, in his recent general account of Harbors (U. S. Geol. Survey, 13th Ann. Rept., 1893, 180 ), suggests that the greater inflow of the tides in the middle of the curved bays between the capes would cause a lateral current in either direction, and that the cusps would form where the outward flow from two curves became confluent; but this is contradicted not only by the general southward movement of sands along the shore, but also