Determinant (biology)

“ But it is evident that the modern biology is much less concerned in the mere recognition of these innumerable forms of life, these remotest expressions of the force of evolution, than in the gaining of some adequate conception of their relations, the forces of adaptation that have fitted them for their particular niche in the realm of nature, their relation to the other organisms with which they are associated and which constitute for them a source of support or a menace to existence. ”

“ These determinants control the parts of the developing embryo,—in what manner need not here concern us. The determinants differ among themselves, those of a muscle are differently constituted from those of a nerve-cell or a glandular cell, etc., and every determinant is in its turn made up of minute vital units, which I call biophores, or the bearers of life. According to my view, these determinants not only assimilate, like every other living unit, but they vary in the course of their growth, as every living unit does ”

“ At the outset it was remarked that the phenomena presented by the organic world as a whole, cannot be properly dealt with apart from the phenomena presented by each organism, in the course of its growth, development, and decay. ”

“ Such are, with their successive transformations, the three principal theories, the three great currents between which biology has been tossed to and fro. They are sufficiently indicative of the state of positive science in each age, but one is astonished that they are not more so ”

“ Finally, we discovered that all these peculiarities are subordinate to the fundamental peculiarity, that vital changes take place in correspondence with external co-existences and sequences, and that the highest Life is reached, when there is some inner relation of actions fitted to meet every outer relation of actions by which the organism can be affected. ”

“ So that throughout physiological development, as in evolution at large, the multiplication of effects has been a factor constantly at work, and working more actively as the development has advanced. The secondary changes wrought by each primary change, have necessarily become more numerous in proportion as organisms have become more complex. And every increased multiplication of effects, further differentiating the organism and, by consequence, further integrating it, has prepared the way for still higher differentiations and integrations similarly caused. ”

“ In brief, the function of substitution possessed by the representative element in the processes of mental selection is the substitute for natural selection in the highest representatives of animal life. ”

“ Individuals in whose germ-plasm the determinants of disused organs ascend, and thereby depress the determinants of organs which are still active, are subject to personal selection, and are eliminated. ”

“ Not only are they still in the strictest sense the biological head-quarters: they are also the standard or central type by which we must explain all the rest of nature, both in man and beast, in plant and animal. ”

“ Dealing with biology in its general principles, it concerns us only to notice how specially sensitive are the substances of which organisms are built up to the varied influences that act upon organisms. ”

“ Every desire consists primarily of a mental representation of that which is desired, and secondarily excites a mental representation of the actions by which it is attained; and any such mental representations of the end and the means, imply antecedent experience of the end and antecedent use of the means. To assume that in the course of evolution there from time to time arise new kinds of actions dictated by new desires, is simply to remove the difficulty a step back.
§ 146. Changes of external conditions are named, by Dr. Darwin, as causes of modifications in organisms. ”

“ We are limited, not by the nature of our method, but by the whole nature of the case, to the comparison of organisms such as are manifestly related to one another and belong to the same zoological class. ”

“ Such a method of evolution and growth is not possible in the vegetable or animal kingdom, where instinct is the only means for the transmission of acquired knowledge. It is this feature that differentiates man from all other created beings. ”

“ All other things continuing the same, every additional faculty by which an organism is brought into relation with external objects, as well as every improvement in such faculty, becomes a means of subjecting the organism to a greater number and variety of external stimuli, and to new combinations of external stimuli. ”

“ And yet, though not surprising, this attitude of mind, in face of organic phenomena, is illogical, and is due partly to a misconception of the function of scientific interpretation, partly to influences arising from the course pursued by the historical development of scientific knowledge. The function of biological science is to formulate and to express in generalized terms the related antecedences and sequences which are observed to occur in animals and plants. ”

“ Passing now to the causes of variation, all of the countless deviations of living things can be referred to three kinds of primary factors; namely, the environmental, functional, and congenital influences that work upon the organism in different ways and at different times during its life. We shall learn that the evolutionary values of these three classes are by no means equal, but we take a long step forward when we realize that among the things we see every day are facts demonstrating the reality of three kinds of natural powers quite able to change the characters of organic mechanisms. ”

“ In the mental life of animals the same factors of evolution exist as those by means of which organic structures have been brought into existence, and it is reasonable to suppose that the operation of these factors have produced in the mental world results analogous to those produced by the operation of the same factors among organic structures. ”

“ In other words, to understand Natural Selection we must recognize not only the facts thus expressed, but the factors of these facts,—we must analyze the “conditions of existence.” As a preliminary analysis we find external conditions, among which are included not only the dependence of the organism on the inorganic medium, but also the dependence of one organism on another,—the competition and antagonism of the whole organic world ”

“ And the presence, in all kinds of animals and plants, of functionally-useless parts corresponding to parts that are functionally-useful in allied animals and plants, while it is totally incongruous with the belief in a construction of each organism by miraculous interposition, is just what we are led to expect by the belief that organisms have arisen by progression. ”

“ This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called "natural selection, or the preservation of favoured races in the struggle for life." ”

“ The chief evidences of the theory of descent are to be found in homologies, in the correspondences of organs and functions, as revealed by comparative anatomy and physiology, in the recapitulation revealed by embryology, in the structure of parasites, in rudimentary organs and reversions to earlier stages, in the distribution of animals and plants, and in the possibility of still transforming, at least to a slight extent, one species into another, by experimental breeding.
Transformation and differentiation go on in nature as a vast, ceaseless, but blind process of selection. ”

“ But if this is the answer we have passed at once from the realm of observation to the realm of fancy—to a realm that is foreign to our experience; for such a view assumes that chemical and physical reactions are guided by the needs of the organism when the reactions take place inside living beings. ”

“ In order to place the phenomena of instinct upon the same footing, with reference to natural selection, as is held by other manifestations of life, it is only necessary to show that instincts vary, and that these variations may become hereditary. ”

“ For the rest, it has at least been made evident, by all that has been said above concerning the constant contact and interaction of organism and environment, that the selection of one of these two factors as the positive and one as the negative, one as the formative the other as the formed, one as the active the other as the passive factor, one as independent the other as dependent, one as invariable the other as alone variable, is an arbitrary one. ”

“ That many and grave objections may be advanced against the theory of descent with modification through natural selection, I do not deny. I have endeavoured to give to them their full force. Nothing at first can appear more difficult to believe than that the more complex organs and instincts should have been perfected, not by means superior to, though analogous with, human reason, but by the accumulation of innumerable slight variations, each good for the individual possessor. ”

“ Passing by what is here said of the aptitude of the human race to multiply, to spread, to separate, and to differentiate—an aptitude which has never resulted in the production of an essentially different animal, or in anything but incidental variations within the limits of the same species—I propose now to apply to this argument from distribution a test which seems to me to be a perfectly fair one, and one which it ought to be able to encounter. ”

“ Hence, the validity of any hypothesis respecting the one class of phenomena, may be tested by its congruity with phenomena of the other class. We are now about to pass to the more special phenomena of development, as displayed in the structures and functions of individual organisms. If the hypothesis that plants and animals have been progressively evolved be true, it must furnish us with keys to these phenomena. ”

“ Consider instinct, for a moment, as one of the qualities of life. There is given to every insect, fowl, and animal a specific and perfect knowledge. It is limited to-its own wants. Its range is narrow and it cannot be extended; but it is perfect within its limits. It is given round and complete at once. Here we can see that it is a quality of life to give every form it can create, a full and perfect measure of power according to its capacity to receive. ”

“ Where the properties of an object are known to be closely interdependent, as in the organisation of plants, animals and societies, we are especially justified in inferring from one case to another. The whole animal Kingdom has certain common characters—the metabolic process, dependence upon oxygen, upon vegetable food (ultimately) , heredity, etc., and, upon this ground, any process (say, the differentiation of species by Natural Selection) that has been established for some kinds of animal is readily extended to others. ”

“ Finally the curve of mental development caught up with that of body, and intersected it: mind became the dominant factor in the new type of organism, and in the subsequent history of the evolutionary process. The organism ceased to be the highest unit, and gave place to the person, or self-conscious individual with organized mind. ”

“ But it is not sufficient to give the explanation of the cause which has brought about the condition of the organs of different animals—a condition which we see to be always the same in those of the same species; we must besides observe the changes of condition produced in the organs of one and the same individual during its life, by the single result of a great change in the special habits in the individuals of its species. ”

“ I ought to have made this admission expressly; with the reservation, however, that, as far as I can judge, no theory so well explains or connects these several generalizations (more especially the formation of domestic races in comparison with natural species, the principles of classification, embryonic resemblance, etc.) as the theory, or hypothesis, or guess, if the reviewer so likes to call it, of Natural Selection. Nor has any other satisfactory explanation been ever offered of the almost perfect adaptation of all organic beings to each other, and to their physical conditions of life. ”

“ It was this which made us believe that we had found the means to an answer in reason as the cause of action towards ends, as also, again, that we had found it in the development of the higher organism from the lower, and of the organic from the inorganic. We know no such independent cause, no such essence. We know only variables, preceding conditions and succeeding conditions, all of which preceding and succeeding conditions we must regard as equally essential since they are equally actual; and we know in all variation a certain constancy of relations, which we, by abstraction, term law. ”

“ The actions of every part of animal bodies may be advantageously compared with each other. This strict analogy contributes much to the investigation of truth; while those looser analogies, which compare the phenomena of animal life with those of chemistry or mechanics, only serve to mislead our inquiries. ”

“ Biological truths and their corollaries, presented under these special forms as bases for sociological conclusions, are introductory to a more general biological truth including them—a general biological truth which underlies all rational legislation. I refer to the truth that every species of organism, including the human, is always adapting itself, both directly and indirectly, to its conditions of existence. ”

“ All parts of the organism are in a certain degree variable and capable of being determined by the strength and nature of the influences that affect them; and this capacity to respond conformably to functional stimulus must be regarded as the means which make possible the maintenance of a harmonious co-adaptation of parts in the course of the phyletic metamorphosis of a species. ”

“ In the theory of Organic Selection, therefore, we seem to have a positive solution of the question of the origin of instinct. It is capable of a similar application in other cases where evolution has taken certain definite directions, seemingly guided by intelligence. It shows us that mind has had a positive place in the evolution of organic nature.
Animal Intelligence.—Coming to consider what further equipment the animals have, we light upon the fact just spoken of when we found it necessary to appeal in some measure to the animal's Intelligence to supplement his instincts. ”