1 11EP0RT on the DIATOMS of the ALBATROSS VOYAGES in the PACIFIC OCEAN, 1888-1904. by Albert Mann

1 11EP0RT ON THE DIATOMS OF THE ALBATROSS VOYAGES IN THE PACIFIC OCEAN, 1888-1904. By Albert Mann. [Assisted in the bibliography ami citations by P. L. Kicker.] INTRODUCTION. The paper here offered is a report of the diatoms found in the sea dredgings and soundings of the United States Bureau of Fisheries steamer Albatross, which covers all the material collected and available up to January 1, 1005, exclusive of what is embraced in a short report already published by the author.® The preliminary work was done in the Smithsonian Institution, Washington, D. C., during the winters of 1809-1900 and 1904-5. The crude material, as a rule bottled and preserved in alcohol, was first examined under the microscope, using magnifying powers ranging from 23 to 500 diameters, so as to discover which gatherings gave promise of affording dialomaccous material. In very many cases no trace of diatoms was discoverable. The gatherings thus selected were then prepared for more accurate investigation by methods that are briefly described as follows: The mud is first passed through a sieve of bolting cloth with a mesh of about one thirty-second inch, so as to strain out large pieces of for- eign material, such as bits of animal tissue, fragments of shells, etc. The alcohol is then eliminated by washing in filtered or distilled water in a glass beaker and decanting of the liquid after all solid material has settled. The mud is next boiled in a beaker with concentrated commercial hydrochloric acid for one-half hour. The acid when cold is decanted and the residue washed with water to get rid of the resultant salts. The material is then boiled in concentrated commercial nitric acid for fifteen to thirty minutes and again washed. This suffices in aPrnc. I'.-S. \nl. Mux. 16: 3IW-312. 1894. 221 222 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. many instances to destroy all organic matter and to prepare for the further step of separating the diatoms from coarse sand, Iiadiolaria, etc. Often, however, a third treatment is necessary, especially where the percentage of organic matter is high and where clay is present. The third boiling is in concentrated commercial sulphuric acid. As much water as possible is extracted from the mass by careful decantation and removal of the last drops with a pipette. The acid is then slowly added, the quantity being about ten times the volume of the mass, and the whole is boiled in a porcelain evaporating dish over a sand hath for one-half hour. At the expiration of this time powdered potassium chlorate is slowly added to the boiling acid until the black color gives place to a gray or yellow. Very thorough washing follows this to remove the last trace of acids and salts. In those instances where a fine siliceous flock is present, this can be removed by bringing the washed residue to a boil in a solution of soap, made by adding about 5 per cent of a saturated alcoholic soap solution to distilled water. The soap water holds the flocculent matter in suspension and allows its removal by decantation. As, however, very delicate forms like Chaetoceros, Nitzschia, etc., are liable to be lost by this method, it is to be used only where unavoidable. The coarse sand, Radiolaria, and like impurities are now removed by rotating the material in a glass evaporating dish. By quickly revolving the lowest point of the dish in a small circle of, say, one-half inch a peculiar motion is given to the contents, on account of which the large sand and other coarse ingredients collect in a mound at the center, while the diatoms are held in suspension. The liquid is quickly poured off from the sand, the process being repeated until the sand is found under the microscope to be free from diatoms. The cleaned diatoms are then preserved in bottles in a 40 per cent solution of alcohol with distilled water. In the preparations accompanying this report the diatoms were picked up separately with a mechanical finger from strewn masses of the cleaned material and mounted singly in the proper medium, generally Canada balsam. They are attached to the cover glasses of the preparations by a delicate film of acetic-acid gelatin, and so placed as to occupy the center of a minute ring of inilia ink spun on the glass slide. 'I his mounting each specimen separately as a labeled prepara- tion, although involving much labor, was the only satisfactory method of rendering available for future examination the forms herein described. Strewn slides of diatomaceous material containing certain species, like the II. L. Smith type slides and most of those of Cleve and Moller, are valuable; but every student consulting these for identification must have felt the great inconvenience and uncer- tainty of hunting among a mass of mixed diatoms for a certain species, the exact appearance of which is, under the circumstances, not MANN—DIATOMS OF TITE ALBATROSS VOYAGES. 223 known. Only when each species is mounted by itself an<l in such a position on the slide as to he instantly found under the microscope can diatom preparations he considered worthy to be compared with other scientific specimens of reference. In addition to these preparations of single forms, representing each species found, this report is accompanied by a series of group slides of selected forms. Kach of these preparations has from 10 to 100 diatoms, arranged in rows on the cover glass or massed in the center of the india ink ring. Their purpose is to afford a type gathering of each of the more important diatomaceous dredgings and soundings examined. As has been remarked, a large number of the Albatross gatherings were found to be destitute of diatoms. Xaturallv. these barren sam- fc- f pies included most of those obtained at grea-t depths, say 1,200 fathoms and upward. There are, however, many cases where deep dredgings were particularly rich in diatoms, as, for example, station 3<>07, having a depth of 9X7 fathoms, and 3712II, at 1,744 fathoms. It was also found that a considerable number of the gatherings made in shallow water and at points where diatoms would naturally be looked for contained no trace of them. It would certainly be a mis- take to infer from the absence of diatoms in most of the deep-sea gatherings and in many of those from shallower places or from the sea surface that none were present at these points. In many instances their absence is to be explained by the methods by which these gatherings were made. It is evident that devices perfectly adapted to securing larger forms of animal and vegetable life may fail completely to retain any specimens of these very minute plants. The modes of making the gatherings, the way they are brought aboard the ship, and the process of assorting the contents would often elimi- nate all traces of the diatoms, at least of all forms that grow without attachment to other bodies. Diatoms are to be found in richest quantity in the upper and lighter layers of mud of the sea bottoms, and those on the surface of the sea can be secured only when a special appliance is attached to the tow nets. As a consequence, a large majority* of the gatherings now in the possession of the I . S. National Museum are destitute of diatoms, although many of them * were made at points where with different methods rich supplies could have been secured. The cruise of the Albatross under Dr. Alexander Agassiz, just completed, is reported, however, to have resulted in obtaining an unusually rich supply of the diatoms. I have tried to supply this deficiency of diatomaceous material in some of the dredgings by examining the contents of the stomachs of animals, chiefly liolothurians, taken at these points. This is, however, a very partial and unsat isfactory substitute. The stomach contents arc generally rich in diatoms, so far as number of individuals 224 CONTRIBUTIONS PROM TIIE NATIONAL HERBARIUM is concerned; but as the diatoms would find their way into the atom- ^ 4' achs of these animals only in connection with the grosser material on which they feed, the forms thus secured would represent only such as happened to be mixed with or attached to their food. A host of other forms, on or in the sea mud in that vicinity, would therefore be missed entirely. As our Government, so far as I can learn, has not, previously at least to the last cruise just mentioned, made any special effort to collect the diatoms, in connection with its general gathering of other organic forms, I think it will be opportune to point out here the great importance of this work being thoroughly carried on in the future. The Diatomaceae are not only equally worthy of investigation with other forms of plant and animal life as inhabitants of the ocean surfaces and beds, but they have a unique value, shared by no other forms, for determining important questions regarding the extent and direction of ocean currents and the origin of the materials composing the sea bottoms. This comes from several peculiar circumstances affecting the diatoms: The first is the indestructibility of their siliceous remains; whence it results that, unlike most aquatic plants, they are not subject to decay, those which were formed cen- turies ago being as well preserved as those of this year's product. This is also t rue of some other organisms, as the Radiolaria and the siliceous parts of sponges.

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