THE TRANSFORMATION OF ORGANIC DESIGNS: A REVIEW OF THE ORIGIN AND DEPLOYMENT OF THE EARLIER VERTEBRATES
Authors: GREGORY WILLIAM KING 
Published: January 2008

Paley argued that because natural mechanisms often work like human mechanismsthey must have been made by a great designer; but this was an anthropomorphicfallacy which left the time element out of account. Darwin was able to show thatin many cases intergrades are known that connect even the most complex naturalmechanism with simpler antecedents; also his principle of the natural selectionof heritable variations seemed to provide a mechanism for the production ofmechanisms. However, the discovery of great numbers of what have been calledorthogenetic series has obscured the principle that the natural selection of smallheritable variations (mutations of the geneticists) I ˜nservesa nd integrates originallyindependent variables and tends to eliminate aberrant or “fortuitous” variationsand lethals that lie too far to one side of the curve. That there is indeed a subsidiarymechanism for the elimination of the vast majority of merely random variations issuggested by the discovery of “orbhers”, which preside over the course ofdevelopment and tend to keep it within prescribed limits (Spemann, 1927).

It is not, however, the purpose of the present article to discuss the causes ofevolution but merely to formulate in general terms the ways in which organicdesigns of known history have originated and evolved, especially during theemergence and deployment of the vertebrates. An organic design is defined as acollocation of parts of an organic whole, varying in magnitude, emphasis or distancein space or time from the chosen point of origin or reference. As thus defined thechanges in many typical organic designs of known history may all be expressed asthe resultant of two co‐operative principles of individual development and phylogeneticevolution: the first may most briefly be called repetilion, the second emphasis. The principle of repetition has long been recognised in part under such names as “repetitive acceleration” (Cope), “metamerism” (Gegenbaur), “merism” (Bateson), “aristogenesis” (Osborn), while the principle of uneven development or emphasishas been called “differentiation” (Spencer), “alloiometry” (Osborn), “heterogony” (Pézard, J. S. Huqley), and so forth. For some years past the writer has beencalling the products of organic repetition polyisomnes and the general method ofrepetition, budding or reproduction polyisomerish; while for parts or regions that become unevenly developed, increased, decreased or fused with their neighboursthe term anisomeres is employed and the process itself is called anisornetism. Now one and now the other of these processes may predominate, but both are constantlyaltering organic designs to a greater or less degree. The term secondary polyisomerism is used to denote the important fact that when one polyisomere acquires a certaindetailed character its neighbours all along the line usually change in the samedirection. This, as it were, throws a screen of small details over the surface andimparts an often false appearance of simplicity, homogeneity and primitiveness towhat is in reality a very advanced stage of specialisation. When anisomeres areaffected by secondary polyisomerism the pattern tends toward dedifferentiation.

After long periods of divergent evolution each of the diversified descendantgenera of a common stock will be found to be in possession of: (a) a mask of changedorganic designs relating especially to its particular mode of life, which is collectivelycalled its habitus, and (b) a smaller fund of unchanged organic designs or charactRtisticsinherited from the remote common stock, the totality of such charactersbeing called its anatomic heritage. Part of the habitus of a remote common ancestorafter a change of function becomes part of the heritage of its descendants, and thetwo correlative terms may be qualified so as to indicate such conditions as therelative phyletic ages of any particular habitus and heritage, or the relativesystematic values. Thus the swordfish‐like ordinal habitus of ichthyosaurs datesfrom Triassic times, but their reptilian clms heritage is of Permian age; the family habitus of the Macropodidae is kangaroo‐like, but their superfamiZy heritage isphalangeroid, By extension of the same principle we may speak of the habitusand heritage features of some particular division of an organic design, such as thejaws and dentition, the feet, the reproductive system and the like.

Changes in habitus and heritage, if proceeding at slow rates or for relativelyshort periods, often convey the impression of orthogenesis, or undeviating evolution, but by combining the best established results of comparative anatomy and embryologywith the records of palaeontology over long periods of geologic time we discoverthe reality and frequence of the phenomenon of transfomtion.

In reviewing the transformation of organic designs as seen in the deploymentof the vertebrates, the writer holds that his method has on the whole not been a priori, since the foregoing principles were established objectively after the actualhistory of the vertebrates had been illuminated by the largely independent laboursof a great number of geologists, palaeontologists and comparative anatomists, whofor the most part were always interested in solving concrete historical problemsrather than in considering the general principles of evolution. The principles ofrepetition and emphasis, of habitus and heritage, of undeviating evolution, transformationand the like, enable us to conceive the discrete facts of evolution ingeneral terms, but these concepts to be effectively applied must naturally besupplementary to discovery of the historical facts.

With these provisos the writer has given a very brief review of the historicproblem of the origin of the vertebrates, rejecting the claims of various phyla, suchas the annelids, nemerteans, arthropods, etc., on different grounds and showingthat astonishing changes among certain echinoderms from an essentially quinqueradiateto a functionally bilateral symmetry warn us not to overlook thepossibility that the invertebrate ancestors of the vertebrates may not have beenbilaterally symmetrical, fusiform, free‐swimming types but possibly sessile bottomlivingforms with a strong dorso‐ventral asymmetry.

The conclusions reached may be summarised as follows:

Amphioxus is secondarily polyisomerous in many respects and anisomerous inothers, and may well be a degraded and highly specialised derivative of the oldestknown chordates, the ostracoderms.

The contrasts are great between these earliest known chordates and any knowninvertebrates, with the posaible exception of the carpioid echinoderms.

The most primitive of the ostracoderms appear to be among the Heterostraci, especially the poraspids. These are fusiform fishes with an armour of five platescovering the head and front part of the thorax. In the thelodonts and coelolepidsthe shield is represented by a great number of small tubercles or scales which havearisen by secondary polyisomerism from a once continuous head shield (Kiaer).

The Heterostraci have paired nasal sacs, and according to Kiaer are related tothe ancestors of the jaw‐bearing fishes and higher vertebrates. From presentevidence this relationship may well be much closer than would be possible underthe older view that the heterostracous ostracoderms were a highly specialized side branch.

The gnathostomous or jaw‐bearing vertebrates probably arose by transformationfrom agnathous creatures that bore no special resemblance to them except in thepossession of certain “basic patents”, especially the serial gill pouches.

With regard to the origin of the modem Agnatha (lampreys and hagfishes), the superb material and intensive investigations of Stensio leave no doubt that thelampreys are derived from the cephalaspid ostracoderms, a result of great importancein the morphology of the central nervous system, since it confirms the conclusionsof neurologists that the arrangements of the cranial nerves and general brain patternsof the larval lamprey are on the whole much more primitive than those of theelasmobranchs.

The investigations of Patten and Stensio on BothriOZepis and of Stensio on theArthrodira have proved that these long extinct placoderms represented earlyoffshoots from the base of the jaw‐bearing series of classes. They seem to thepresent writer also to be derived eventually from some agnathous but branchiateancestors who could not be very far from the most primitive of the heterostracousostracoderms. Heintz's admirable work an the evolution of the Arthrodira fromthe acanthaspids has also provided a clear example of the interaction of polyisomerisrnand anisomerism.

The same principles are everywhere apparent in the recorded deployment ofthe higher vertebrates, as illustrated by the changes in the body form in the teleosts, or by the strange transformation of the mandible in the ancestry of the mammals.

Thus one may gain a new perspective on the origin of that peculiarly variablesystem of organic designs that has called itself Homo sapiens, who after a prodigiousexpansion of his neopallium began to make organic designs for himself; then, withgrowing pride and egotism and with all the prejudices of his race, nationality andprofession, easily persuaded himself that he was a respectable even if much reducedcopy of a “Great Designer”.