A Mechanico-Physiological Theory of Organic Evolution Part 1

A Mechanico-Physiological Theory of Organic Evolution.

by Carl Von Nageli.

PREFATORY NOTE.

Mr. V. A. Clark, as a student in horticulture in the University of Vermont, first undertook a critical examination of Nageli's _Mechanico-Physiological Theory of Evolution_ as a part of his regular junior work. After a half year's study and the preparation of a short thesis, Mr. Clark had become so far intimate with Nageli's work as to make it seem best for him to continue the study through his senior year.

This study involved extended translations from the text, including Nageli's _Summary_, which, considering its difficult accessibility to American students, has been chosen for publication. The work has been done chiefly by Mr. Clark, but has all been under my immediate supervision, and I have given the whole matter a final restudy and revision. Those who have had any experience with similar work will know how impossible it is that all mistakes should have been avoided, and it would be a kindness to the translators if readers would point out any defects, in order that they may be corrected.

F. A. WAUGH.

University of Vermont, July 1, 1898.

SUMMARY.

In this summary I shall in general pursue a course the reverse of that which my main work follows.[A] I shall proceed from the primitive, unorganized condition of matter and endeavor to show how organized micellar substance has arisen in it, and how, from this micellar substance, organisms with their manifold properties have arisen.

Since such a synthesis of organisms out of known forms of matter and force is still far removed from a conclusion strictly in accord with physical law, the process becomes comprehensible and obvious only by exact knowledge of the discussion that has preceded. Although the synthetic method reveals more clearly the weaknesses of the theory than do a.n.a.lytic investigations, yet I considered it helpful to make this presentation in order to give a clearer idea of the mechanico-physiological theory, and at the same time to test its worth.

[A] See Appendix, Translators' Notes.

1. FORMATION OF UNORGANIZED BODIES (CRYSTALS).

When separated and promiscuously moving molecules of any substance in solution or in a melted condition pa.s.s into the solid form by reason of removal of the causes of separation and motion (warmth or solvent), they arrange themselves into solid ma.s.ses impermeable to liquids. These minute bodies grow by accretion, and when molecular forces are permitted to act undisturbed, a.s.sume the regular outer form and inner structure of crystals. The number of crystals, their size, changes of form and growth, all depend on external conditions.

2. FORMATION OF LIVING ORGANIZED (MICELLAR) BODIES.

Certain organic compounds, among them alb.u.men, are neither soluble, despite their great affinity for water, nor are they fusible, and hence are produced in the micellar form. These compounds are formed in water, where the molecules that arise immediately adjoining each other arrange themselves into incipient crystals, or micellae. Only such of the molecules as are formed subsequently and come in contact with a micella contribute to its increase in size, while the others, on account of their insolubility, produce new micellae. For this reason the micellae remain so small that they are invisible, even with the microscope.

On account of their great affinity for water the micellae surround themselves with a thick film of it. The attraction of these micellae for matter of their own kind is felt outside this film. Hence the micellae with their films unite themselves into solid ma.s.ses permeated with water, unless other forces overcome attraction and re-establish a micellar solution (as in alb.u.men, glue, gum), where the slightly moving micellae show a tendency to cling together in chain-like and other aggregations. Very often there are found, especially in alb.u.men, half liquid modifications intermediate in fluidity between the solid ma.s.ses and the micellar solution.

The internal and external const.i.tution of micellar bodies depends essentially on the size, form and dynamic nature of their micellae, since these efficients condition the original arrangement of the micellae and the insertion in proper order of those formed later. External conditions have slight influence on structure, and affect outer form chiefly in so far as they can mechanically hinder free development.

The micellae of alb.u.men or plasma are susceptible of the greatest diversity of form, size and chemical composition, since they originate from unlike mixtures of various alb.u.men compounds, and besides are mixed with various organic and inorganic substances. For this reason the plasma behaves, both chemically and physically, in many unlike ways, and in consequence of the variable relation of the micellae to water, the plasma shows all degrees of micellar solution up to quite solid ma.s.ses.

3. SPONTANEOUS GENERATION. LIFE. GROWTH.

If molecular forces are so combined in an inorganic substratum that spontaneous formation of alb.u.men takes place, then by the combination of the micellae the primordial plasma ma.s.ses of spontaneous generation are given. Within these plasma ma.s.ses the production of alb.u.men goes on more easily under the influence of their molecular forces than in the liquid without. Hence the compounds present in the organic substratum and capable of forming alb.u.men enter preferably into the ma.s.ses of plasma, and by intussusception of micellae of alb.u.men, cause growth. Here life exists in its simplest form. (See page 47.)

Spontaneous generation presupposes the origin of plasma-micellae from molecules, and hence cannot be brought about by solutions of alb.u.mens or peptones, since these are micellar solutions. Life presupposes the intussusception of plasma-micellae; hence it ceases as soon as the arrangement of micellae is so far disordered by injurious influences that that process of growth becomes impossible.

The resulting organism must be perfectly simple, a ma.s.s of plasma with micellae as yet unarranged, because any organization without a preceding organizing activity is inconceivable. For this reason known organisms cannot have orginated spontaneously; a kingdom of simpler beings must have preceded them (_Probien_--the sub-organic kingdom).

The growth of the ma.s.ses of plasma continues as long as the conditions of nutrition are favorable. If these become unfavorable, a resting period (latent life) or partial or total death occurs, according to circ.u.mstances (as lack of nutritive material, lowering of temperature, comparative exsiccation). The growth of plants and animals is nothing else than the continuation of the growth begun in the primordial plasma.

This growth still continues wherever the primordial plasma exists.

4. PARTIAL DEATH OF THE INDIVIDUAL: REPRODUCTION.

Since the primordial ma.s.ses of plasma continue to attract nutritive materials indefinitely and apply them to growth, the nutritive materials are used up in one place and another and the substance which is no longer nourished is in great measure disintegrated. A general condition of equilibrium now sets in, in which the viable plasma ma.s.ses continue to gain just as much in growth as there is dead plasma broken down and changed back into the original nutritive materials.

In the primordial condition this balancing process is irregular and accidental and remains so even later in many of the lowest organisms.

Little by little it becomes phylogenetically more regular by individuals attaining to a more definite size and term of life, while only the germs detached from them remain viable. This phenomenon known as reproduction has a double origin.

_A._ The portions of primordial plasma that grow to a more considerable size as soft, half-liquid ma.s.ses break up by the mechanical action of external circ.u.mstances into smaller portions of indefinite number and size. This typifies irregular and accidental reproduction of the lowest order.

In the offspring of the primordial plasma division becomes gradually more and more regular as a result of the increasing organization of the substance, and especially as a result of the formation of an envelope about it, till finally in the microscopically small ma.s.ses, which are now called cells, division into two parts always appears, after these ma.s.ses have grown to perhaps double their original size. After division the two halves separate from each other and represent independent individuals.

In the further course of phylogeny the division of the cells into two parts takes place regularly. But the cells remain united to each other and form multicellular individuals, which increase by cell division and which at times in the lowest stages are divided at regular intervals into smaller individuals, perhaps even at last into single cells, but from which there are periodically given off cells that develop as germ cells into new multicellular individuals.

_B._ Another phenomenon which appears in the primordial plasma or its immediate offspring is the death of the greater part of the plasma under certain unfavorable conditions of nutrition, while the smaller part continues to be nourished at its expense and in that case remains viable during the dormant period.

In the offspring this phenomenon gradually becomes free cell formation, which takes place before the resting stage or before the death of many unicellular and multicellular organisms, and which forms germ cells from a part of the contents of the parent cells.

The formation of germ cells by cell division (_A_), or by free cell formation (_B_) is reproduction of the organism. The germ cells are the elements in which the life and growth of the parental individual are continued.

5. MORPHOLOGY OF THE IDIOPLASM IN GENERAL.

The larger part of the unarranged, soft and h.o.m.ogenous primordial plasma, which grows by intussusception, becomes watery soma-plasm, with unarranged and easily movable micellae. The smaller part is converted in the course of phylogeny into idioplasm, in which at certain favorable points the micellae that are being stored up under the influence of molecular forces arrange themselves into groups by similar orientations, and hence form bodies of less water content and greater solidity. Each body of idioplasm consists originally of only one group of micellae, which, however, necessarily breaks up with increasing additions into several groups. On account of the dynamic influence of the groups of micellae upon their own growth, they become in part more distinct and more definitely separated, in part again differentiated by new irregular intussusception. This phylogenetic process is continued indefinitely, by which the combination of forces produces a new configuration, and conversely, by which a new configuration produces a new combination of forces, so that the body of idioplasm merely takes on a continually increasing complexity of configuration by the action of the internal forces--that is, by the molecular forces of the micellae of the alb.u.men under the influence of which growth proceeds. This const.i.tutes the _automatic perfecting process_ or progression of the idioplasm, and entropy of organic matter. (See p. 47.)

The above described phylogenetic perfecting process of the idoplasm, which operates through internal causes, is scarcely affected by differences of nutrition and by climatic conditions influencing nutrition. On the other hand all those external forces which act as stimuli during a long period of time in an unvarying manner have a very noticeable influence on the intussusception of micellae in the idioplasm and on the molecular processes going on among the micellae. The action of stimuli determines the particular structure of the groups of micellae added under the direction of the perfecting process. Thus the configuration of the idioplasm becomes continually more and more complex and at the same time a.s.sumes a local adaptation corresponding to external conditions. This const.i.tutes adaptation of the idioplasm.

6. FUNCTION OF THE IDIOPLASM IN GENERAL.

The unarranged micellae of the alb.u.men of the spontaneously generated plasma are as yet in no way superior to the unorganized condition from which they have arisen, except in this that under the influence of their molecular forces the formation of similar new alb.u.men micellae follows more easily. But as by the further action of molecular forces idioplasmic bodies are formed with groups of smilarly oriented micellae, the molecular forces of these micellae amount by summation to molar forces and thereby new chemical processes are introduced; plastic products are formed from plasmic and non-plasmic materials, and molar movements are introduced. And since idioplasmic bodies are formed under the influence of external stimuli, their plastic products always appear with a definite character of adaptation to environment.

Then, as the idioplasmic body becomes continually more complex in the further course of phylogeny, and consists of a greater number of groups of micellae differing from each other, the organisms become more complex and differentiate into a greater number of parts, because each group of micellae of the idioplasm produces its specific effect with regard to inner structure, outer form, and function.

7. DETERMINANTS: THEIR ORIGIN AND DISAPPEARANCE.

Since a particular cl.u.s.ter or group of micellae of the idioplasm produces a particular phenomenon in the organism, the former is designated as the determinant (_Anlage_, see p. 49) of the latter. Thus the organism must contain at least as many determinants in its idioplasm as there are different phenomena in its inheritable ontogeny; and if new phenomena appear in it, new cl.u.s.ters of micellae must previously have been introduced into the idioplasm, or the orientation and arrangement of cl.u.s.ters already present must have been changed. The formation of such a determinant, whether it concerns the perfecting of the organism or its adaptation to environment, always proceeds very slowly, and as a rule has no effect before its completion. Hence along with perfected determinants the idioplasm always contains growing and incomplete determinants.

If a phylogenetic line comes under the influence of other external conditions and other external stimuli than those which have hitherto acted upon it, a new and corresponding arrangement of the micellae appears phylogenetically in the idioplasm. At the same time the other adaptation determinants remain either undisturbed, or the new determinant is formed at the expense of related determinants which are already present and which may at last entirely vanish. Hence along with growing and complete determinants the idioplasm always contains likewise weakened and vanis.h.i.+ng determinants. From the fact that a phylogenetic race is thrown repeatedly among different external conditions, it may at last unite in its idioplasm a large number of developing, mature, and vanis.h.i.+ng adaptation determinants. This number is noticeably increased if in consequence of interbreeding a fusion of related idioplasms take place.

8. DEFINITE NOTIONS WITH REGARD TO THE MORPHOLOGY OF THE IDIOPLASM.

Since in the phylogenetic development of the plasma the thicker idioplasm is differentiated from the more fluid soma-plasm (-- 5), the former has the tendency by nature to a.s.sume a reticular arrangement. The strands of this network consist, in conformity with their origin, of parallel rows of micellae extending lengthwise. These rows of micellae are combined into more or less complex arrangements, so that the cross section of the strand represents the configuration of the idioplasm.[B]