« AnteriorContinuar »
northeast and southwest. The Marble, for instance, ran from Virginia, through Teneessee, to Georgia, a distance of more than one hundred and fifty miles. How much further it extended lengthwise beyond the limits of Tennessee, I know not. Yet with this length its greatest breadth was not more than twenty miles. There can be no question as to the beltlike character of this bed when first deposited. Although broken and dislocated by after movements, the original thinning out of the bed laterally is clearly seen in good sections.
The ferruginous bed commenced within the limits of Tennessee, a few miles above the present site of Knoxville, and ran down into Georgia. Its length in Tennessee was not less than 100 miles. How far it extended south westward into Georgia, I have not ascertained. It covered a somewhat wider area than the marble, but had very much the same long belt-like character.
To what now is the long narrow form of these beds to be attributed ? and why did they, or do they, conform in direction to the great Appalachian folds ? and why did they thin out on both sides much after the same manner, there being, at this period, no greater indication of dry land on one side than on the other? It appears to me that your view of the Silurian age of the Appalachian oscillations will alone satisfactorily account for these characters. By them the sea-bottom was arranged (perhaps in a long trough) first for the crinoidal grove, the remains of which, together with small corals, (Chaetetes,) form the Marble bed. Afterwards by other oscillations the bottom and the sediment were prepared for the ferruginous bed, &c.
There are other facts bearing upon this subject, which I have observed in the Lower Silurian rocks of East Tennessee, but which time will not permit me to refer to at present.
3. Post-Pliocene of Lewiston, Maine.—Mr. W. W. Baker gives an account in the Proceedings of the Boston Soc. Nat. Hist., 1858, p. 394, of the occurrence of a fossil starfish in a hill of earth, 30 miles from the sea, 200 feet above its level, 100 feet above the level of the Androscoggin, which is half a mile off, and 10 feet below the present level of the surface. The hill is clay for eight feet, then thin layers of sand, gravel and clay, alternating. The species according to Mr. Bouvé, was the same as the living species of the coast. There were also numerous impressions of shells.
4. Untersuchungen über die Entwickelungs-Gesetze der organischen Welt, während der Bildungs-Zeit unserer Erd-Oberfläche, by Dr. H. G. Bronn: 502 pp. 8vo. Stuttgart, 1858.—This work is a general review of the progress of life in the course of geological history. It received the prize from the French Academy in 1857.
5. Further Contributions to the Palæontology of the Tilestones or Silurio-Devonian Strata of Scotland ; by Mr. D. Page, (Proc. Brit. Assoc., Ath., No. 1616).- Without entering on the stratigraphical relations of these tilestones (which would be discussed at a subsequent meeting), he might simply mention that part of them, as in Lanarkshire, seemed to cap and form portion of the Upper Silurians, while the larger portion, the Forfarshire flagstones, undoubtedly constituted the basis of the Old Red Sandstone; hence, with a view to avoid all discussion in the mean time, he had ranked the whole as “ Silurio-Devonian.” Beginning with the Lanarkshire beds, he had, since the Glasgow meeting, been enabled to add several new forms to the fossil Fauna of that district, for hitherto no trace of vegetation had been detected in the strata. In addition to Trochus helicites and Lingula cornea, which were then known, he had now to add Pterinea, Orthonota, Nucula, Avicula, Orthoceras, and other well-marked Ludlow or Upper Silurian shells. To the Crustaceans then known, viz., Beyrichia, Ceratiocaris, and Himanthopterus, he had now to add several discoveries which rendered the structure of these curious crustaceans more apparent, besides the detection of two entirely new forms, which he would venture to term provisionally Eurypterus spinipes and E. clavipes, in allusion to the characteristic form of their swimming paddles, or third pair of organs wbich spring from the under side of their cephalothorax. Turning to the Forfarshire beds, which in 1855 were known to yield little more than obscure vegetable forms, Parka decipiens of Lyell, Pterygotus, and Cephalaspis, he was now enabled to add several new and gigantic forms of Fucoids, a Cyclopteris, and a Lepidendroid stem, which was clearly of terrestial origin. To the Fauna he has added gigantic Scolites or annelid burrows, Serpulites or annelid tracks, and an organism which appeared to be the remains of an annelid itself. There had also been discovered several new portions of Pterygotus, which rendered the true structure of that gigantic crustacean much more apparent; and he had also been enabled to describe and figure two new crustaceans under the names of Kampecaris and Stylonurus, the latter closely related in structure to Eurypterus, and approaching the forms of those found in the Lanarkshire strata, To Cephalaspis, of which little more was known than the head and bony ring-plates of the body, he had now to add a well-marked corneous eye capsule, a pair of pectoral fins, a dorsal fin, and the true form of the large heterocercal tail,—so that, instead of figuring this much-caricatured fish as had hitherto been the case, as a saddler's knife for the head, and a parsnip with a few radicles for the body, we could now restore it as a legitimate and elegant fish, much resembling in general contour the armed bullhead or Aspidophorus of our present shores. There had also been discovered a vast number of fin-spines or Ichthyodorulites, which were yet undescribed, and a small fish with tin-spines and shagreen-like scales, to which he had given the name of Ictinocephalus granulatus, in allusion to its kiteshaped head and shagreen-covered body. For the discovery and preservation of these new fossil forms, palæontologists were mainly indebted to James Powrie, Esq., of Reswallie, Forfar, and to Mr. Slimon, surgeon, Lesmahagow, to the latter of whom the British Association, on the representation of Mr. Page, has given a grant of 201., to assist in prosecuting his researches among these interesting but as yet partially explored strata.
III. BOTANY AND ZOOLOGY. 1. Nereis Boreali- Americana ; or Contributions to the History of the Marine Algæ of North America ; by William Henry HARVEY, M.D., M.R.I.A., F.L.S., Professor of Botany in the University of Dublin, etc. Part III. Chlorospermec. (Smithsonian Contributions, for 1858). Pp. 140, tab. 37–50, imp. 4to.–Our readers are familiar with the first part of this elaborate work, containing the Melanospermea or olive-colored
Algæ, and with the second, the Rhodospermeæ, or rose-red series. With the Chlorospermeæ, or proper green Algæ, Dr. Harvey has now completed this extensive undertaking, and furnished us with a manual of the highest character, by which the marine Algæ of our continent,—and also a good part of the fresh-water species--may be readily studied. Great praise and cordial thanks are due to Dr. Harvey for the prolonged and assiduous labors which have fairly opened this wide and difficult field to the American student; and likewise to the Smithsonian Institution, for its enlightened liberality in the publication, not only presenting copies to all the principal public libraries of the world, but placing a separate edition upon sale at a low price, which brings the work within the reach of every earnest student or zealous amateur in the country. We are gratified to learn that the enterprise and good judgment of the managers of the Institution are duly appreciated by the public; and that the work has achieved a popularity unsurpassed by any of the valuable Smithsonian Contributions to Knowledge.
No good account of the Chlorospermece could be given without some view of the fresh-water species also. So, as many of these as was possible under the circumstances, have been included in the present memoir. But a large part of them can be investigated only when alive. Also the Diatomacece and Desmidiaceæ, although they systematically belong to the Algoe, yet they form a microscopic world of themselves, and require a separate treatment by a special monographer. The accomplished naturalist upon whom this task appeared to devolve, and who, indeed, had done much towards its accomplishment, is no more; he of whom our author feelingly writes, in the following extract.
“I must therefore leave the task of (more fully] describing the freshwater Algce of America to other hands ;--to soine one living among them; and having eyes fully open to the difficulties of his task, and zeal and ability to work it faithfully. And here I cannot omit a slight tribute to the memory of one in whom were combined, in no common degree, the qualifications which make an able naturalist, and who, had he lived, would probably have taken up the broken thread. I allude to the late Professor J. W. Bailey, of West Point, one of the earliest explorers of American Alge, and whose very able memoirs on the Diatomacece have won for him an imperishable name in the annals of science. To me his loss is more personal than to most of his botanical friends; for, from the hour we first met there grew up between us a warm friendship, which death has interrupted, but which I trust it has not ended. He it was who first suggested to me a memoir on the American Algæ; he arranged with the Smithsonian Institution the terms of its publication; he supplied me with a multitude of specimens; and to his influence I owe the assistance I have received from many American algologists, who looked up to him for direction in their studies. He was, as far as the Algæ are concerned, my chief American referee, to whom I could apply when seeking information on local matters connected with this branch of study. With him I constantly associated my work, and to his approbation I looked forward as the most grateful reward of my labors; and now that he is removed, my interest in the work has sensibly flagged, and I am not sorry that it is brought to a conclusion.”
A passing tribute is paid to the memory of another contributor, the late Professor Tuomey of Alabama; and his name is commemorated in one of the two new genera described in the present part. Tuomeya fluviatilis is a fresh water plant, resembling a Lemanea in external appearance, but very different and not a little curious in anatomical structure.
The other new genus, Blodgettia, is named for the late Dr. Blodgett of Key West, who had zealously collected the Algæ as well as the other plants of the Florida Keys.
The structure of Blodgettia confervoides (which is illustrated in one of the plates) is so extraordinary and unexpected, that we are tempted to copy the account of it. Briefly, the cell-wall of its unicellular joints is “ formed of separable membranes, the outer of which are hyaline and homogeneous, the innermost traversed by parallel, longitudinal, anastomosing veinlets. Spores seriated in moniliform strings, developed from the veinlets of the inner cell-wall!” The following is the detailed account.
“The highly curious little Alga on which the present genus is founded so closely resembles a Cladophora that it will readily pass for one, unless it be very closely examined under a powerful microscope. Iudeed so great is the resemblance to a branched Conferva that I formerly distributed it to my friends with the manuscript name of Cladophora cæspitosa, under which it was my intention to have described it in the present work; nor did I discover my error until I commenced making sketches for the plate now given. I was then first struck by the peculiar opacity of the dissepiments; and afterwards by what looked like a compound cellular structure in the walls of the cells.
On applying a higher power, other characters came out which induced me to dissect one of the articulations, when I discovered the curious structure of the inner membrane or primordial utricle; in which (as far as I can make out) the spores are developed. To see the structure as above described, the readiest mode is to proceed as follows. Cut off a portion of one of the long cells which terminate the branches ; place it on the table of a dissecting microscope, moisten it, and you may readily express the viscid endochrome, which generally contains, besides the usual starch and chlorophyll grains, a number of pyramidal crystals; but these are probably adventitious. When the endochrome has been pressed out, the structure of the inner cell-wall may be partially sean; but to see it clearly, the outer coats must be removed. This may readily be done, either by tearing, with a pair of dissecting needles, or by making a longitudinal section through the cell, when the different coats easily separate, on the section being teased in a drop of water. The outer coat, coats (for there are two or more, though the secondary ones sometimes elude detection, owing to their extreme tenuity) are quite transparent and structureless, as is usually the case in the walls of cellular tissue. But the inner coat offers a peculiarity of structure which I have not noticed in any other Algæ, nor have heard of its occurrence in the cells of any other plants. At first sight the membrane seems to be composed of numerous minute, elongated fusiform cellules, not unlike the wood-cells of phanerogamous plants, but totally unlike any algæ cells known to me. Careful examination has however convinced me that the appearance of cellular
structure is deceptive; and that the membrane itself is homogeneous, but traversed by slender filiments or nerves, which anastomose together, forming areola which look like cells. These filiments give off free ramuli whose apices swell into spores; and (probably) by repeated cell division produce the strings of roundish spores, which are so conspicuous in most of the areolæ. The appearance of the whole membrane with its spores is as if a number of the asci of a lichen were placed side by side; the true structure, however, I need hardly say, is widely different.”
Truly nature revels in variety, in the lowest and simplest, even more than in the highest tribes of plants. Hydrodictyon, or the Water-net, affords another, and a more familiar illustration of this, being a viviparous Alga. While in a Conferva a zoospore develops into an individual which increases in dimensions by the multiplication of its cells, in Hydrodictyon a great number of zoospores combine to form one individual, composed of a definite number of cells which remain unchanged, until each cell gives birth to a new Hydrodictyon complete.
“In all stages the Hydrodictyon is a bag-like or purse-shaped net, with generally five-sided meshes,—each mesh consisting of a single articulation or cylindrical cell, united by its ends to the neighboring cells, ..... and from first to last carrying on an independent existence. When first emitted from the parent, the young Hydrodictyon is of microscopic size. It grows rapidly until each articulation becomes from a quarter to half an inch in length, and half a line in diameter. Up to this period the cells are filled with a green semi-fluid endochrome, in which grains of different sizes are formed. Gradually this green matter is resolved into an infinite number of minute zoospores, which are at first spherical, afterwards ovate, pointed at one end, and which, while contained within the cellwall, exhibit lively movements. At length these movements gradually subside, and the zoospores arrange themselves, end to end, into polygonal, commonly pentagonal areola; and when all the zoospores contained within a single articulation have so arranged themselves, the little net is completed before its emission or birth. When all is thus ready the parent net falls to pieces, each articulation floating separately; and shortly afterwards, on the bursting or deliquescence of the wall of the mother-cell, the little net work floats independently, and commences its career of growth and development.”
Here only the spores or germs are active; the developed plant vegetates quietly. But in the Oscillatorias, which are described a little further on, the mature plant exhibits very animated movements. “Some have a rapid progressive and regressive movement, by which they can change their place, rising or falling in the water; others, while remaining nearly in one place, move from side to side, describing an arc. The genus Oscillatoria is so named from the pendulum-like movements of its filaments. Species of this genus are to be found in most pools of stagnant water, and their peculiar movements may be easily observed. These plants occur, when fully developed, in floating, skin-like, slimy pellicles, of a deep green, or blackish, or bluish color, and a gelatinous substance. If a small portion of the floating scum be placed in a cup of water, and allowed to remain for some hours at rest, its edges will become finely fringed with delicate, radiating threads, which extend further and further SECOND SERIES, Vol. XXVII No. 79.-JAN, 1869.