Metamorphism

“ The operation of metamorphism is therefore another serious difficulty in the way of recognising the oldest rocks. The earliest animals and plants which have been discovered are not such as we should expect to find as examples of the first products of organic life. ”

“ The evidence of organic origin is perhaps not conclusive, and in the present state of knowledge it is certain to be met with much scepticism, more especially by certain classes of specialists, whose grasp of knowledge is not sufficiently wide to cover, on the one hand, fossilization and metamorphism, and on the other, to understand the lower forms of life. ”

“ It therefore seems best for me to confine my remarks to the reasons usually advocated for the imperfection, namely, the lack of hard parts in many animals, metamorphism, the frequent imperfect preservation of fossils, and the unrepresented time in the geologic column.
The lack of hard parts in many animals is a serious, although not fatal, objection to their preservation as fossils. For the best results as fossils, a stony framework of some kind is desirable, as we all know, but horny, or even the most perishable materials may be preserved under favorable conditions. ”

“ Only rarely, however, does metamorphism produce much difference in the chemical composition of the rocks affected. Sandstones become quartzite’s and quartz schists, limestones are converted into marbles, granite passes into gneiss, and so on, without their bulk composition being greatly modified. From all that we know it seems established that however great the heat and pressure to which metamorphic rocks have been exposed they have very rarely been melted or reduced to the liquid state. ”

“ A review, however, of the facts of hypermetamorphism, particularly the life-history of Mantispa, throws much light on the subject, since it is very probable that the supernumerary stages and marked changes of form characterizing them are due to changes of environment, of habits, and of food, causes which have exerted such a profound influence on organic beings throughout all time. ”

“ The dogma of creation, the mystic and dualistic doctrine of the isolated creation of each separate variety, was annihilated at one blow; the belief in transmutation has now for ever taken its place—the mechanistic and monistic doctrine of the metamorphosis of organic forms, of the descent of all the species of one natural class from a common parent-form. How complete a change the science of mechanical morphology has by this means been compelled to undergo, I have endeavoured to point out in my "General Morphology;" ”

“ It seems to be a general fact that a structure which in metamorphosis disappears completely may easily be omitted altogether in embryonic development, while one which is modified into something else continues to pass more or less through its original larval condition. ”

“ In the first place, I must remark that these human remains, which are in my possession, are characterized, like the thousands of bones which I have lately been disinterring, by the extent of the decomposition which they have undergone, which is precisely the same as that of the extinct species: all, with a few exceptions, are broken; some few are rounded, as is frequently found to be the case in fossil remains of other species. ”

“ The close analogy between evolutionary and transcendental morphology has already been remarked upon and illustrated in the last three chapters. We have seen that the coming of evolution made comparatively little difference to pure morphology, that no new criteria of homology were introduced, and that so far as pure morphology was concerned, evolution might still have been conceived as an ideal process precisely as it was by the transcendentalists. The principle of connections still remained the guiding thread of morphological work ”

“ Pure morphology is essentially a science of comparison which seeks to disentangle the unity hidden beneath the diversity of organic form. It is not immediately concerned with the causes of organic diversity—that is rather the task of the sciences of the individual, heredity and development. To take an example—the recapitulation theory may legitimately be used as a law of pure morphology, as stating the abstract relation of ontogeny to phylogeny, and the probable line of descent of any organism may be deduced from it, as a mere matter of the ideal derivation of one form from another ”

“ To metamorphosis he only allowed a logical value, as explaining the natural classification; the only real, existent metamorphosis he saw in the development of the individual from its embryonic stage. Still more distinctly did he contravene the general tendency of scientific explanation. “It is held the triumph of science to recognize in the general process of the earth the same categories as are exhibited in the processes of isolated bodies. This is, however, an application of categories from a field where the conditions are finite to a sphere in which the circumstances are infinite.” ”

“ The morphology of the 'fifties lent itself readily to evolutionary interpretation. Darwin found it easy to give a formal solution of all the main problems which pre-evolutionary morphology had set—he was able to interpret the natural system of classification as being in reality genealogical, systematic relationship as being really blood-relationship; he was able to interpret homology and analogy in terms of heredity and adaptation; he was able to explain the unity of plan by descent from a common ancestor, and for the concept of "archetype" to substitute that of "ancestral form." ”

“ The close affinity of transcendentalists and evolutionists is shown very clearly in their common contrast in habits of 305thought with the Cuvierian school. It is the cardinal principle of pure morphology that function must be excluded from consideration. This is a necessary and unavoidable simplification which must be carried out if there is to be a science of pure form at all. But this limitation of outlook, if carried over from morphology to general biology becomes harmful, since it wilfully ignores one whole side of life—and that the most important. ”

“ Morphology then is not only a study of material things and of the forms of material things, but has its dynamical aspect, under which we deal with the interpretation, in terms of force, of the operations of Energy. And here it is well worth while to remark that, in dealing with the facts of embryology or the phenomena of inheritance, the common language of the books seems to deal too much with the material elements concerned, as the causes of development, of variation or of hereditary transmission. ”

“ What, then, is the significance of all these facts, and why should we gather them from the highways of morphology but for the lesson which they teach, that all forms of animals, plants, rocks, and stars are traced to the substrate of extension in the particle? Extension traced through all its complicated relations of space, form, metamorphosis and organism is found to be the ultimate substrate of them all. ”

“ Any form or condition of structure under a species which differs in its characteristics from those typical to the species, as in color, shape, size, and the like, and which is capable either of perpetuating itself for a period, or of being perpetuated by artificial means; also, any of the various forms under a species meeting the conditions mentioned. A form characterized by an abnormity of structure, or any difference from the type that is not capable of being perpetuated through two or more generations, is not called a variety. ”

“ Here we have seen the same organ is formed «?» «for» different purposes «ten words illegible»: and if, in several orders of vertebrata, we could trace origin «of» spinous processes and monstrosities &c. we should say, instead of there existing a unity of type, morphology{154}, as we do when we trace the head as being the vertebræ metamorphosed. Be it observed that Naturalists, as they use terms of affinity without attaching real meaning, here also they are obliged to use metamorphosis, without meaning that any parent of crustacean was really an animal with as many legs as crustacean has jaws. ”

“ For all practical purposes, however, the empirical laws of co-ordination of structures, which are embodied in the generalisations of morphology, may be confidently trusted, if employed with due caution, to lead to a just interpretation of fossil remains ”

“ As previously stated, I propose to adopt the term Heteromorph for a confusion with one another of two or more different skeuomorphs, or with the amalgamation of any two or more biomorphs, or with the combination of any skeuomorph with any biomorph. We may thus have (1) Heteromorphs of skeuomorphs, (2) Heteromorphs of biomorphs, and (3) Heteromorphs of skeuo-biomorphs.
To speak somewhat figuratively, heteromorphism is a sort of disease that may attack the skeuomorph or the biomorph. ”

“ Any stage of the life-history of a biomorph, whether it is the expression of decorative or religious art, is liable to be infected by heteromorphism. The only section of graphic art which must from the nature of the case be free from it is pictorial art. Where heteromorphs are introduced into pictures they form one of the subjects of those pictures, the picture itself is not subject to this modifying influence; for example, the introduction of the representation of a sphinx or a gryphon into a picture does not constitute the latter a heteromorph. ”

“ But in the case of animals with a metamorphosis, the mortality among the larvæ, always considerable, must have become still greater under new than under accustomed conditions, every step towards the simplification of the process of development must therefore have given them a still greater preponderance over their fellows, and the effacing of the metamorphosis must have gone on more rapidly. What has taken place in each individual case, whether the species has immigrated after it had lost the metamorphosis, or lost the metamorphosis after its immigration, will not always be easy to decide. ”

“ But it is not: instances are not uncommon in which organisms, having attained to a certain degree of complexity and heterogeneity of structure, subsequently, as a consequence of adapting themselves to their environment, lose it and revert to an earlier stage of development, relatively simple, homogeneous, and structureless. Such reversion or regressive metamorphosis is as much a part of the organism's evolution as its previous progressive metamorphosis; and progress and regress both are equally the result of adaptation to environment. ”

“ Natural as may seem the assemblage included under Arthropoda, there is no group in which adaptive modifications have introduced so much diversity of anatomical and physiological relations. Metamorphoses, the changes of form which changes of external conditions have promoted, are met with of very various amount. The progress of the embryo from the first appearance of the blastoderm up to sexual maturity of the adult may be direct, without metamorphosis, or may be retarded by changes of form and habit, rendering the young animal capable of sustaining life under very various conditions. ”

“ But if such a metamorphosis as this is possible—if the seemingly wide gap between leaf and stamen may be spanned by the modification of a line of organisms—where does the possibility of modification of organic type find its bounds? Why may not the modification of parts go on along devious lines until the remote descendants of an organism are utterly unlike that organism? Why may we not thus account for the development of various species of beings all sprung from one parent stock? ”

“ Although man is, zoologically considered, only a higher animal, it is convenient to retain the term “anthropomorph,” which has been used by some writers to express representations of the human form. All three terms have reference to living beings, hence the appropriateness of classing them under the general designation of “biomorph.” The biomorph is the representation of anything living in contradistinction to the skeuomorph, which, as we have seen, is the representation of anything [127] made, or of the physicomorph which is the representation of an object or operation in the physical world. ”

“ The conception of a morphological type, which was then supported in England by the great influence of (Sir) Richard Owen [q. v.] , may be understood from his definition of homology, which he interprets 'as signifying that essential character of a part which belongs to it in its relation to a predetermined pattern, answering to the "idea" of the archetypal world in the Platonic cosmogony, which archetype or primal pattern is the basis supporting all the modifications of such part ... in all animals possessing it' (Owen, On the Nature of Limbs, 1849) . ”

“ Accordingly, form is one of the least important elements to be considered in determining a homology. "Nature," he wrote in one of his early papers, "tends to repeat the same organs in the same number and in the same relations, and varies to infinity only their form. In accordance with this principle I shall have to draw my conclusions, in the determining the bones of the fish's skull, not from a consideration of their form, but from a consideration of their connections." ”

“ The product will appear as in infinite metamorphosis.
(From the stand-point of reflection, as continually on the leap from fluid to solid, without ever reaching, however, the required form.—Organizations that do not live in the grosser element, at least live on the deep ground of the aërial sea—many pass over, by metamorphoses, from one element into another; and what does the animal, whose vital functions almost all consist in contractions, appear to be, other than such a leap?) ”