Review of Zoonomische Briefe
|Review of Zoonomische Briefe|
Zoonomische Briefe : Allgemeine Darstellung der thierischen Organization. Von Dr. Hermann Burmeister, Professor der Zoologie zu Halle. Erster und Zweiter Theil. 8vo. Otto Wigand: Leipzig. 1856. Not addressed directly to the professed Zoologist, these outlines of the chief types of animal structure, and of the relation that they bear to the general system of nature, are intended for a class—even now increasing in number—who, prepared already by a certain amount of education, have come to regard the observation of nature as a part of the habitual exercise which conduces to the full development of the faculties, and are willing to include the study of the laws of Life and Organization among the acknowledged instruments of intellectual training. As to the epistolary form into which they have been thrown, this appears to have scarcely any object but that of interrupting the long-drawn chain of systematic analysis by convenient pauses, and, perhaps, of occasionally relieving the monotony of comparative descriptions, by falling into a tone more colloquial than might have appeared to suit a formal lecture or a scientific essay. But the work does not assume, or affect, the anecdotical character of some books that are termed popular, by courtesy, we suppose, on the strength of being only superficial. The writer's thorough acquaintance with his subject, at once minute and comprehensive, his genuine—even passionate love of nature, and his eminently happy style of painting in words, have qualified him, without renouncing a scientific treatment of his materials, to make out of them two very pleasant volumes, for those, at least, in whom a taste for the exact observation of nature has been in some degree awakened, and who do not feel it a painful stretch when they are obliged to concentrate their attention, and to reflect and compare, as well as perceive and remember.The author's design, not less than the compass of the work, has excluded,for the most part, those circumstantial examples among which popular books of Natural History delight to revel ; but these have not been superseded for the sake of introducing some questionable speculations,or investigations of a difficult and slippery sort. If elsewhere Burmeister,in the pursuit of a natural classification, may have appeared sometimes to attach undue importance to the earlier stages of structural development, in comparison with the finished type to which, in every instance, they may be viewed as continually tending ; yet here, at least, his riper judgment and experience has revolted against the fixed ideas of some extreme devotees of Embryological study ; and he appeals from their verdict, who can see nothing in animated "nature more profoundly significant than their ciliary epithelium" and the "segmentation process." Whatever may be thought of the freaks of fancy that some of its votaries have indulged in, however we may reprobate the perversions of truth and common sense which have been engrafted on it in certain quarters, this much is fairly to be said of the Transcendental school of Natural History, that its original principles were calculated to suggest, to a reverential spirit, some of the most striking arguments which Natural Theology has to offer for the infinite wisdom and universal agency of one God. Nay, they seem to be such as can scarcely fail to excite some notions of this sort in any unprejudiced mind, even when the distinct acknowledgment of that presiding intelligence is most studiously eschewed by the teachers of natural science, and although "God", "Creation", and " Providence" be set aside for such equivocal terms as "Nature," "Law", or "Necessity". It might appear, too, as if the systematic part of Natural History were thus placed on a more unalterable base, in being referred to certain principles exterior to and independent of the modes of operation of the human intellect ; as a mere artificial instrument of which classification has sometimes been regarded. It is all the more surprising to find Burmeister,who has laboured before so hard, and, as many may think, so successfully—whatever he himself may judge of it now—to establish a natural classification on philosophical grounds, in the present work almost giving up the objective truth of natural groups in zoology, while he retains them for a method of exposition. " The only real existence is the lowest and last division, called Species ; this alone can be seen, felt, caught,exhibited in collections;—all the other superior groups are mere conceptions, framed according to the agreement of certain characters, but of which the real existence must be denied. There exists neither Bird nor Fish, but only a Sparrow, a Crow, a Hen ; or a Carp, a Pike, a Herring, &c. —the first three are Birds, the others Fishes, but none of them a mere Bird, or a mere Fish." The fallacy here is so palpable that it is hard to comprehend how it could for a moment have imposed upon a philosopher like Burmeister. The argument—if it is good for anything, and not a mere play upon words—goes equally to negative the real existence of species. After he had said, a little way back, that in an army the individual soldier alone has a real existence, why not affirm that individual animals alone exist, and not species—that no one is a mere man, but also John, or James, &c that is, distinguished by some marks—be they but particular existence in a definite portion of space and time—from every other man. It is clear he has mystified himself by an equivocal use of the term," real existence." He proceeds— " Such conceptions, which have no real existence, but can be defined ideally by a certain collection of characters, are called Types of Animal Organization. Accordingly, we speak of the types of Genus,Family, Class, &c, and we endeavour to discover by observation the essential properties of each, and to express them in words. These words constitutethe character of the group ; they convey the definition of the idea, and contain the marks by which the type may be known, and which, therefore, are considered as typical of the group." This, we see, is in allusion to, but not quite in accordance with, the doctrine of Linnaeus, that the character does not make the genus, but the converse. That very real existence of species, to which Burmeister yet clings—as it seems, however,not without a wavering faith even as to this—as the last floating straw of a drowning system is just as truly an abstraction of the mind as any of the higher groups. Define it as we will, the idea of species comprehends some relation which cannot be seen, felt, or exhibited corporeally—such as that of continuous generation from one stock ; or, if we admit that no irrefragable proof has yet been adduced of the necessary descent of all the individuals of a species from one original pair, or parent, then our idea of species must differ still less in kind from that of any higher group. We must be able to conceive, as possible at least, if we do not actually assume as true, the original existence of several individuals and one species, to which they are subordinated not by that peculiar relation of Generation, but by other agreements, of the same sort, and only greater, in number or degree, than, those we recognize among the higher groups, and in the one case as in the other, coupled with Differences ;—whether these be Specific, Generic, or simply Individual, does not materially affect the present question. In this case, whether we trace these correspondences up to Creative Design, or view them simply in reference to our own Modes of Perception, the result is equally that those Relations and Agreements,and, consequently, also the Groups connoted, or denoted, by the character,have a Real existence as truly in the Higher (genus, &c), as in the Lower(species)—yet not Lowest group so long as some individuals of the Species present fewer differences and more points of agreement among themselves (Races, Varieties, &c), than others. Again, whatever be our Idea of "Species" abstractedly, the Character of any particular species is a collection of marks of a precisely similar nature with those which make up the character of a Genus, or any higher group, differing only in being more numerous and particular, inasmuch as the character of the Species includes the complete character of the Genus, and of every higher group, in direct ascending Series, and something more. In Direct ascending Series—we repeat—for the Character of some genus, in another, i.e. Collateral series, may embrace more numerous marks than that of a Species not subordinate to it. Practically, too, it is the character that determines the idea of the species, which is then of the same sort as that of genus, &c, and applied in the same way, so that it is hard to tell why the one should be said to have a real existence more than the other.It is, of course, only in one point of view that Burmeister disputes the existence of Natural groups. That there are natural groups, according to the perceptions of our own minds, seems to need no further proof than the universal method of human language (admissible evidence in a question of this nature), and the fact of our being able to make any true general propositions concerning the things we observe in nature, of such a sort as form the basis of Burmeister's own graphic sketches, which, if sufficiently divested of technical affectation to be both attractive and intelligible to all who have availed themselves of the advantages of a liberal education, are, at the same time, imbued with such intrinsic learning, that the most advanced need not disdain to study them, for the sake of their own proficiency as well as delight. We fear our readers will think we have been prolix in this dry discussion of the point on which we have ventured formally to dissent from the view that Burmeister has taken here. We find a much more agreeable employment in turning to the body of the work, to which we can offer the meed of almost unqualified commendation. The matter here is too condensed—the phrase too pregnant—to admit of further abridgment for the purpose of areview. As a specimen of the author's manner, we extract the concluding section of the history of the Polyps :— "The study of the formation of corals at the epochs anterior to history, or, if another form of expression is preferred, in pre-Adamitic times, is a subject of the deepest interest for the geologist. It shows him the wonderful activity of these minute creatures on the largest scale, while it proves the complete agreement of organization between the most ancient Polyps and those in being at the present time. In all periods, going back to the most remote antiquity of the globe, there have been Polyps in our terrestrial seas, at least as long as organic life has existed on the earth at all. It is corals that furnish the most ancient evidence that the earth was inhabited long before the beasts came into existence. The organization of these primitive corals agrees completely with those now living. We meet, indeed, in the oldest strata, with genera distinct from, yet closely resembling, those of the present day ; but even at that period all the existing families were represented. In general the oldest forms of corals appear as flatter, lower, more solid stems, inhabiting the bare rocky coasts, in that period before a strand was formed, where they multiplied to a vast extent ; but in consequence of the disconnected form of the rocks to which they were affixed, they formed, as we see, no such great mural reefs as in later times, when the unbroken lines of coast descending sheer into the sea, with a rocky bottom, afforded a more suitable foundation to build up their stony walls. Certain members, however, of the oldest Silurian Calcareous rocks—as the limestone of Dudley, Schonen, Reval, Eifel (at Bensberg in particular)—seem to be chiefly formations of coral, which, if not constructed quite as solid reefs, are yet principally composed of the fragments of polypidoms. It is remarkable that the shells of the Polythalamia, so abundant in recent times, are almost entirely wanting in the most ancient coralline limestones. The most probable explanation is the absence of flat coasts at that remote date ; since the Foraminifera occur only in such situations, and at the present day inhabit in the greatest numbers the lagoons of the coral islands, or the channel between the reefs and the land to which they form a barrier.There do not seem at that early period to have been any shallows of this sort."
" The coral formation shows itself in uncommon plenitude in the calcareous rocks which constitute the base of the Carboniferous system. The Mountain limestone, as well as the Dudley limestone, is at least partially, a vast coral bank, to the formation of which the calcareous shells of Foraminifera have largely contributed."
" Similar phenomena continue to occur in the calcareous formations of later date, almost all the sedimentary rocks of this class presenting local evidences of ancient coral formations, being composed chiefly of the stems and not of mere debris of corals. We may cite, for instance, the remarkable Dolomites of Lubenstein and Altenstein, Konitz and Posneck, at the south-western extremity of the Thuringian forest, not far from Salzungen, which are standing yet unmistakeable rocks of coral, the reefs that once bordered the narrow island ridge of that district, like those of the southwest coast of New Caledonia at the present day. This is another evidence that the former temperature of those seas was much higher than that now prevailing in the Temperate Zone; as the coral animalcules cannot live below 20°-23° of heat by Reaumur's scale. None but warm seas have coral reefs, and even there only in particular situations favourable to their formation."
" The extensive system, denominated the Muschel-Kalk, is singularly characterized by the scarcity of its corals ; in no portion of it is there any unequivocal evidence of the existence of coral reefs. This formation seems to have been a purely sedimentary deposit, the organic fossils of which belong chiefly to the class Mollusca, as the name itself (shell limestone) indicates."
" The coral banks of the Jura are developed in inverse proportion to this last. No other formation affords such decisive evidence of the effective part which the coral animals have taken in the formation of the upper strata of the globe. The members of this group, in their protracted parallel layers and defined terraces, exhibit, in unaltered position, walls of rock built up entirely of coral, and, at the foot of these, huge masses of coral debris which have been cemented by finely comminuted particles of lime, telling of the raging surf that broke against those reefs in days of old. These fragments are intermixed with other fossil remains varying with the localities, and form united a motley conglomerate, which is known under various names, but most commonly as Coral Breccia. Generally, the coral reefs of the Jura have more the character of Barrier reefs, and they seem to have extended parallel to the coast at a moderate distance from it, as exemplified in the coral reef of New Caledonia. Such a reef extended, during the Jurassic period, right through the south of Germany and the west of Switzerland, from the neighbourhood of Geneva away to Ratisbon, and thence northwards to the river Main, between Bamberg and Baireuth."
"Not less extended was the system of coral reefs in the succeeding Cretacean period, the greatest part of the chalk being derived from corals, at least as a deposit. In the chalk period there existed already large land-locked seas, such as the Red Sea at present ; and on the shores of these the coral animalcules wrought in undisturbed tranquillity, and in concert with innumerable Polythalamia, deposited the whole mass of the white chalk, which is more than five hundred feet in thickness. The effective part which the Polythalamia have had, ever since, in the formation of the calcareous rocks, shows that flat tracts of coast have prevailed extensively. We have compared the terraces of the Jura to Barrier reefs, in the chalk we find more resemblance to the Lagoon reefs (" Atolls") ; although the chalk basins were not, strictly speaking, Lagoon islands, but rather were formed as promontories of pre-existing higher lands, contiguous to great bays of the ocean."
" Subsequent to this period, the formation of coral reefs took place only in particular localities, as we find it at the present day. The Tertiary period presents no more vast calcareous formations of coral purely ; the function of the coral animals in depositing lime has become more of a local nature, confined to some favourable situations ; while the secretion of lime by the Polythalamia, an agency which was wholly unknown at the earliest epoch, assumes a more and more predominant influence in the formation of the surface of the globe, as we approach the present times. The Nummulite limestone of the Mediterranean beach, the Calcaire Grossier of the Paris basin, the Molasse of Switzerland, and the sub-Appenine limestones, are composed almost entirely of the shells of these minute, but tough creatures, whose indefatigable industry has furnished one of the best and most important of building materials for the use of man. Almost the whole of Paris is constructed of the shells of Foraminifera, and the material of the Egyptian pyramids themselves is a limestone, accumulated ages ago, of countless millions of Nummulites."
"I have now, my friend, set before you, as I consider, the most essential and interesting facts in the Natural History of the Polyps ; but you may still be curious to know on what the little creatures live, as this has not been mentioned yet, although their alimentary organs have been described before. There can be no doubt that their chief food consists of living animals, and that the Polyps, in general, swallow these whole, having drawn them within their reach by means of the current created in the water by their cilia, or having caught and benumbed them with their stinging lines. This may be easily verified in the freshwater Hydra. The stomach, in most of the marine Polyps, is generally found empty, and seldom filled with any large bodies. They must be able to endure long abstinence, and content with small particles of food. What means, indeed, have they to master the larger animalcules ? The current which they create, their chief means of obtaining aliment, is too feeble to overpower those of any bulk, neither are their tentacles long enough to reach and envelope such. Vegetable matter does not seem to enter into their alimentary cavity, probably because it is not fit for their sustenance. There are, indeed, plants floating freely in the sea, but this only in a few situations, and these are far too bulky to be swallowed by a Polyp, while it has no organs with which to detach from them smaller portions. A Polyp cannot gnaw, but is obliged to wait till a piece comes adapted to his swallow ; and that is much more likely to be an active moving animalcule than an alga spore, the only vegetable substance to be had in any quantity in the sea. I think we may safely conclude, therefore, that the food of all Polyps consists chiefly of living animals of no considerable size, and that, in particular, the small and partly even microscopical Tunicata, the fry of Mollusca, the minute marine Annelids and Crustacea which illuminate the surface of the ocean by night with innumerable sparkles of phosphorescent splendour, constitute the principal substances which the Polyps assimilate for their sustenance and growth."
The arrangement of the Animal world, which Burmeister follows in the present work, is, in a great measure, an amplification, and a more scientific filling up of the sketch which forms the concluding portion of his "History of the Creation," in the shape it wears in the latest edition. In the main, he has not departed from the principles of the classification proposed, a quarter of a century since, in his " Class-book of Natural History," and which was exhibited more at large in the " Manual of Natural History," 1837. The investigations of late years, so diligently pursued, and with such fruitful results, regarding the structure and history of the lowest classes of animals, it is true, have afforded much new materials, of which he has not been slow to avail himself here ; but this has tended rather to complete what remained imperfect, and to elucidate that which was obscure heretofore, than to effect a revolution in the ground plan of the system generally. Accordingly, we find the Bryozoa still ranked among his Polyps, yet not without a distinct acknowledgment of the tendency among them to bilateral symmetry, which, with certain other characters, has induced some of the most accomplished zoologists of the present day to place them rather in the Molluscan series, and next to the Tunicata. The Rotifera are still arranged under Crustacea, and the Myriapoda continue associated with the Arachnida. The Polypi and the Acalepha, among the Regular animals, are treated with much particularity and some apparent predilection ; all these, as well as the Irregular animals, in the first of these two volumes. The Symmetrical animals commence with the second volume. For the specialities in the class Mollusca, Burmeister has availed himself of the able assistance of his former pupil, Dr. Giebel. The classification of the Worms is, perhaps, the portion of the work which is stamped most strongly with originality. Commencing, as is usual, with the intestinal worms (Helminthes), the most simple of the class in their organization, Burmeister adopts the conclusions of Lieberkuhn, assigning a place, the lowest, among them, to certain Unicellular animals (Monocystis,&c.) ; the Gregarinae following next,—while he disposes of the Psorospermia in a somewhat different way, as merely embryo forms of these. With the Trematodes and Planarise the Leeches also are associated in one order (Platodes), Flat worms. The Round worms (Gymnodermi) include the families Siphunculini, Priapulidae, and Echiuridae,—all comprehended under the common appellation of Mud worms (Gephyrei), —as well as the proper Nematodes. In the remaining order, Annelides, Burmeister's divisions do not vary materially from the views of Grube, except as regards the removal of the Leeches from this order by the former.
The two volumes published bring us as far as to the end of the Arachnida. There remain, then, of Arthropoda the entire vast class Insecta, and the sub-kingdom Vertebrata, for the subject matter of another volume. Burmeister has briefly indicated here the mode of treatment he contemplates in regard to these ; the space reserved for the Insects being very strictly limited, in consideration of the length at which he has handled them already in other works devoted to that class specifically. The promised appearance of the concluding volume is postponed, however, until the author's return from the second travels, which he has newly undertaken, in South America. We will not here anticipate the criticisms we may be again obliged to enter into, when Burmeister shall have reached the culminant point in the scale of animal organization, at the deferred conclusion of the " Zoonomic Letters f for he has betrayed, of late, a wavering in his allegiance to the views he had embraced before, in common with all the most eminent names in Zoological science, touching another doctrine of not less interest than that agitated in the earlier letters, and on which we have already remarked. Bather let us wish him, on his distant pilgrimage, health and the bland favour of propitious elements ; along with which, large gatherings of scientific fruit, for the materials of future instruction and entertainment of many readers, and ourselves included. A. H. H.