Tell me where is fancy bred,Or in the heart or in the head?How begot, how nourished?Reply, reply.It is engendered in the eyes,With gazing fed; and fancy diesIn the cradle where it lies.
Tell me where is fancy bred,Or in the heart or in the head?How begot, how nourished?Reply, reply.It is engendered in the eyes,With gazing fed; and fancy diesIn the cradle where it lies.
Tell me where is fancy bred,Or in the heart or in the head?How begot, how nourished?Reply, reply.It is engendered in the eyes,With gazing fed; and fancy diesIn the cradle where it lies.
Tell me where is fancy bred,
Or in the heart or in the head?
How begot, how nourished?
Reply, reply.
It is engendered in the eyes,
With gazing fed; and fancy dies
In the cradle where it lies.
But is it fair thus to characterize the “common ancestors” of Transformism as figments which, like all other abstractions, have no extramental existence apart from the concrete objects whence they were conceived? To be sure, their claim to be real entities cannot be substantiated by direct observation or experiment, and so a factual proof is out of the question. Man, the late-comer, not having been present at the birth of organic forms, can give no reliable testimony regarding their parentage. In like manner, noa prioriproof from the process of inheritance is available, because heredity, as revealed to us by the experimental science of Genetics, can account for specific resemblances only, and cannot be invoked, at present, as an empirically tested explanation for generic, ordinal, or phyletic resemblances. It has still to be demonstrated experimentally that the hereditary process is transcendental to limits imposed by specific differentiation. There remains, however, thea posterioriargument, which interprets homology and adaptation as univocal effects ascribable to no other agency than the dual process of inheritance and variation. What are we to think of this argument? Does it generate certainty in the mind, or merely probability?
A moment’s reflection will bring to light the preliminary flaw of incomplete enumeration of possibilities. To suppose that inheritance alone can account for structural resemblance is an unwarranted assumption. Without a doubt, there are other similifying influences at work in Nature besides inheritance. True, inheritance is one possible explanation of the similarity of organisms, but it is not theonlyone. Even among the chemical elements of inorganic nature we find analogous uniformities or “family traits,” which, in the absence of any reproductive process whatever, we cannot possibly attribute to inheritance. Mendeléeff’s discovery of the periodicity of the elements, arranged in the order of their atomic weights, is well-known. At each interval of an octave, a succession of chemical types, similar to those of the preceding octave, recur. Hence elements appearing in the same vertical column of the Periodic Table have many properties in common and exhibit what may be called a family resemblance. Now, we have in the process of atomic disintegration, as observed in radioactive elements and interpreted by the electronic theory of atomic structure, a reasonably satisfactory basisupon which to account for the existence of these inorganic uniformities. Here analogous chemical constitution, produced in accordance with a general law, results in uniformity that implies a similar, rather than an identical, cause. The hypothesis of parallelistic derivation from similar independent origins accounts quite as well for the observed uniformities as does the hypothesis of divergent derivation from a single common origin. Why, then, should we lean so heavily on the already overtaxed principle of inheritance, when parallelism is as much a possibility in the organic world as it is an actuality in the inorganic world?
As to the contrast here drawn between inheritance and other similifying factors, it is hardly necessary to remark that we are speaking of inheritance as defined in terms of Mendelian experiment and cytological observation. In the so-called chemical theory of inheritance, the distinction would be meaningless and the contrast would not exist. Ehrlich’s disciple, Adami, sets aside all self-propagating germinal determinants, like the chromomeres, in favor of a hypothetical “biophoric molecule,” which is to be conceived as a benzine-like ring bristling with sidechains. Around this determining core the future organism is built up in definite specificity, as an arch is constructed about a template. Adami has merely applied Paul Ehrlich’s ideas concerning metabolism and immunity to the question of heredity, commandeering for this purpose the latter’s entire toolkit of receptors, haptophores, amboceptors, etc., as though this grotesque paraphernalia of crude and clumsy mechanical symbols (which look for all the world like the wrenches of a machinist, or the lifters used by the cook to remove hot lids from the kitchen range) could throw any valuable light whatsoever on the exceedingly complex, and manifestly vital, phenomenon of inheritance. It does not even deserve to be called a chemical theory, for, as Starling correctly remarks concerning Ehrlich’s conception, “though chemical in form,” it is not so in reality, because “it does not explain the phenomenon by reference to the known laws of chemistry.”(Cf.Physiology, ed. of 1920, p. 1084.) In a word, the theory of heredity, which seeks to strip inheritance of its uniqueness as a vital process by identifying it with the more general physicochemical processes occurring in the organism, is a groundless speculation, that, far from explaining, flouts the very observational data which it pretends to elucidate.Kurz und gut!to requite the mechanist, Schäfer, with his own Danielesque phrase, here, as elsewhere, the mechanists have succeeded in extracting from the facts, not what the facts themselves proclaim, but what preëxisted in their own highly-cultured imaginations so well-stocked with cogs, cranks, ball bearings, and other æsthetic imagery emanating from polytechnic schools and factories.
But in arguing from the existence of parallelism in the inorganic world to its possibility in the organic world, we are less liable to displease the mechanists than those other extremists, the neo-vitalists, who will be prone to deny all parity between living, and inanimate, matter. Fortunately, we are in a position to appease the scruples of the latter by referring to the facts ofconvergenceas universally accepted evidence that the phenomenon of parallelism occurs in animate, no less than inanimate, nature. Admitting, therefore, that the laws of organic morphology are of a higher order than those which regulate atomic, molecular, and multimolecular structure, these facts attest, nevertheless, that parallelisms arise in organisms of separate ancestry which are due, not to heredity, but to the uniform action of universal morphogenetic forces. Hence general laws can be invoked to account for organic uniformities with the same right that they are invoked to account for resemblances existing between the various members of a chemical “family” like the Halogens. And why should this not be so? Organisms have much in common that transcends any possible scheme of evolution and that cannot be brought into alignment with the position arbitrarily assigned them in the evolutionary family-tree. They all originate as single cells. Their common means of growthand reproduction is mitotic cell division. This leads to the production of asomatella, among the protista, and of asomadifferentiated by histogenesis into two or three primary tissues, among the metista. All these fundamental processes are strikingly uniform throughout the entire plant and animal world. In these universal properties of living matter, therefore, we have a common basis for general structural and organizational laws, which, though irreducible to the “common ancestors” of Transformism, is quite adequate to account for both the homologies and analogies of living matter. Accept this basis of general laws regulating the development of living matter, and there is no difficulty in seeing why the problems posed by exposure to analogous environmental conditions are solved in parallel fashion by organisms, irrespective of whether they are nearly, or distantly, related in the sense of morphology. Transformism, on the other hand, can only account for homology at the expense of convergence, and for convergence at the expense of homology. So far as a common ancestral basis is concerned, the two kinds of resemblance are, from the very nature of the case, irreducible phenomena.
It is only, in fact, by surrendering the principle that similarity entails community of origin, and by falling back on the suggested common basis of general laws, that Transformism makes room in its system for the troublesome facts of convergence. “It might be reiterated in passing,” says Dwight, “that this ‘convergence’ business is a very ticklish one. We have been taught almost word for word that resemblance implies relationship, or almost predicates it; but according to this doctrine it has nothing to do with it whatever.” (“Thoughts of a Cath. Anat.,” p. 190.) And in a subsequent chapter he says: “No very deep knowledge of comparative anatomy is needed for us to know that very similar adaptations for particular purposes are found in very diverse animals. The curious low grade mammal, theOrnithorhynchus, with a hairy coat and the bill of a duck, is a familiar instance. Weall know that the whales have the general form of the fish, although they are mammals, and going more into details we know that the whale’s flipper is on the same general plan as that of the ancient saurians.... The origin of the eye, according to evolutionary doctrines, has been a very difficult problem, which gets worse rather than better the more you do for it. Even if we could persuade ourselves that certain cells blundered along by the lucky mating of individuals in whom they were a bit better developed than in the others till they came to form a most complicated organ of sight, it would be a sufficient tax on our credulity to believe that this could come off successfully in some extraordinary lucky species; but that it should have turned out so well with all kinds of vertebrates is really too much to ask us to swallow. But this is not all: eyes are very widely spread among different classes of invertebrates. More wonderful still, the eyes of certain molluscs and crustacea are on stalks, and this is found also in various and very different families of fishes. How did this happen? Was it by way of descent from the molluscs or the crustacea? If not, how could chance have brought about such a similar result in diverse forms?” (Op. cit., pp. 233-236.)
It may be objected that the resemblances of convergence are superficial analogies, not to be confounded with fundamental homologies. This contention may be disputed; for, as we shall see in the next chapter, there are cases where the convergence is admittedly radical, and not merely superficial. The distinction, moreover, between shallow and basic characters is somewhat arbitrary, and its validity is often questionable. When the skeletal homology that relates the amphibia to the mammals, for instance, is traced to the root of the vertebrate family tree, we find it all but disappearing in a primitive Amphioxus-like chordate, whose so-called skeleton contains no trace of bone or cartilage. Hence, if we go back far enough, the homologies of today become the convergences of a geological yesterday, and we find the vertebratetype of skeleton arising independently in reptiles, mammals, amphibia, and fishes.
Again, there are times when convergent analogies appear to be more representative of the common racial heritage than the underlying structure itself, tempting the evolutionist to fly in the face of the orthodox interpretation, which rigidly rules out analogy in favor of homology, and refuses to accept the eloquent testimony of a remarkable resemblance merely because of a slight technical discrepancy in the structural substrate. A large pinching claw, or chela, for example, occurs in two organisms belonging to the phylum of the arthropods, namely, the lobster and the African scorpion. Both chelæ are practically identical in structure, but, unfortunately, the chela of the lobster arises from a different appendage than that from which the scorpion’s chela emerges. If they arose from corresponding appendages, they would be pronounced “homologous organs” and acclaimed, without hesitation, as strong evidence in favor of the common origin of all the arthropods. In proof of this, we call attention to the importance attached to the adaptations affecting homologous bones in fossil “horses.” As it is, however, the two chelæ are analogous, and not homologous, organs. Hence, technically speaking, the two chelæ are utterly unrelated structures. To the eye of common sense, however, the likeness appears to be far more important than the difference, and the average person will be inclined to view the resemblance as evidence of a community of type. In fact, the tendency to discard superficial, and to retain only fundamental, uniformities, is dangerous to the theory of Transformism. When we confine our attention to what is really basic, we find that the resemblances become so generalized and widespread that specific conclusions as to descent become impossible, and we lose all sense of direction in a clueless labyrinth of innumerable, yet mutually contradictory, possibilities.
Finally, it may be noted in passing that, though it iscustomary with evolutionists to regard homologous characters as the tenaciously persistent heritage of primeval days, and to look upon adaptational characters as adventitious and accessory to the aforesaid primitive heritage, the supposedly older and more fundamental characters fail to give, by the manifestation of greater fixity, any empirical evidence whatever of their being more deeply or firmly rooted in the hereditary process than the presumably newer adaptational characters. We have, therefore, no experimental warrant for appropriating homologous, rather than adaptational, characters to the process of inheritance. “It is sometimes asserted,” says Goodrich, “that old-established characters are inherited, and that newly begotten ones are not, or are less constant, in their reappearance. This statement will not bear critical examination. For, on the one hand, it has been conclusively shown by experimental breeding that the newest characters may be inherited as constantly as the most ancient.... While, on the other hand, few characters in plants can be older than the green color due to chlorophyll, yet it is sufficient to cut off the light from a germinating seed for the greenness to fail to appear. Again, ever since Devonian times vertebrates have inherited paired eyes; yet, as Professor Stockard has shown, if a little magnesium chloride is added to the sea water in which the eggs of the fishFundulusare developing, they will give rise to embryos with one median cyclopean eye! Nor is the suggestion any happier that the, so to speak, more deep-seated and fundamental characters are more constantly inherited than the trivial or superficial. A glance at the organisms around us, or the slightest experimental trial, soon convinces us that the apparently least important character may reappear as constantly as the most fundamental. But while an organism may live without some trivial character, it can rarely do so when a fundamental character is absent, hence such incomplete individuals are seldom met in Nature.” (Science, Dec. 2, 1921, p. 530.)
But, whether it be upon, or beneath, the surface, similitude ofany kindsuffices to establish our contention that inheritance is not the only similifying influence present in organisms, and that resemblance is perfectly compatible with independence of ancestry. We have, therefore, an alternative for inheritance in the explanation of organic uniformities, and by the admission of this alternative, which, for the rest, is factually attested by the universally acknowledged phenomena of convergence, the inference of common descent from structural resemblance is shorn of the last remnant of its demonstrative force, as ana posterioriargument.
But a still more serious objection to the evolutionary interpretation of homology and preadaptation arises from its intrinsicincoherency. Evolution, as previously stated, is assumed to be the resultant of a twofold process, namely,inheritanceandvariation. The first is a conservative and similifying process, which transmits. The second is a progressive and diversifying process, which diverts. To the former process are due the uniformities of homology, to the latter the deviations of adaptation. Upon the admission of evolutionists themselves, however, neither of these processes behaves in a manner consistent with its general nature, and both of them are flagrantly unfaithful to the principal rôles assigned to them. Nowadays the hereditary process transmitsadaptational, as well ashomologous, characters. If, then, adaptational characters are more recent than homologous characters, there must have been a time when inheritance ceased tosimilifyand become adiversifyingprocess by transmitting what it did not receive from the previous generation. There were times when, not content with simply reiterating the past, it began to divert former tendencies into novel channels. In other words, inheritance becomes dualized into a paradoxical process, which both perpetuates the old and appropriates the new. The same inconsistency is manifest in the process of variation, which capriciously producesconvergent, no less thandivergent, adaptations. In two fundamentally identicalstructures, like the wing of a bird and the foreleg of a cat, variation is said to have produced diverse adaptations. In two fundamentally diverse structures, like the head of an octopus and the head of a frog, variation is said to have produced an identical adaptation, namely, the vertebrate type of eye. It appears, therefore, that the essentially diversifying process of variation can become, on occasion, a simplifying process, which, instead of solving environmental problems in an original manner, prefers to employ uniform and standardized solutions, and to cling to its old stereotyped methods. Inheritance similifies and diversifies, variation converges and diverges. It is futile to attempt to reduce either of these protean processes to a condition that even approximates consistency. The evolutionist blows hot and cold with the same breath. Verily, his god is Proteus, or the double-headed Janus!
Summa summarum: The evolutionary argument from homology is defective in three important respects: (1) in its lack of experimental confirmation; (2) in its incomplete enumeration of the disjunctive possibilities; (3) in its inability to construct a scheme of transmutation that synthesizes inheritance and variation in a logically coherent, and factually substantiated formula. The first two defects are not necessarily fatal to the argument as such. Though they destroy its pretensions to conclusiveness, they do not preclude the fulfilment of the moderate claim made in its behalf by Prof. T. H. Morgan, who says: “In this sense (i.e., as previously stated) the argument from comparative anatomy, while not a demonstration, carries with it, I think, a high degree of probability.” (“A Critique of the Theory of Evolution,” p. 14.) The third defect is more serious. The apparently irreducible antagonism which the evolutionary assumption introduces between inheritance and variation has been sensed even by the adherents of transformism themselves, and they have searched in vain for a formula, which, without sacrificing the facts, would bring into concord the respective rôles of these discordant factors. “It follows,” says Osborn, “as an unprejudicedconclusion from our present evidence that upon Weismann’s principle we can explain inheritance but not evolution, while with Lamarck’s principle and Darwin’s selection principle we can explain evolution, but not, at present, inheritance. Disprove Lamarck’s principle and we must assume that there is some third factor in evolution of which we are ignorant.” (Popular Science Monthly, Jan., 1905.) The point is well taken, and unless, as Osborn suggests, there is atertium quidby means of which the discord can be resolved into ultimate harmony, we see no way of liberating the theory of Transmutation from this embarrassing dilemma.