cultivation make this method of obtaining proper food for Cladocera perhaps less useful in some cases than the one now to be described. It seemed desirable to have a culture medium which could be readily obtained anywhere and at any season of the year. Such a medium has been obtained as follows: two pounds of fine garden soil are placed in a large battery jar (9 in. diameter); to this are added six ounces of finely divided fresh (8 to 15 days old) horse manure and the whole is covered with 10 quarts of strained pond water. Pond water is specified because Cladocera are extremely susceptible to the toxic effects of the salts of the heavy metals. Tap water should be used with caution until proved innocuous. The mixture is allowed to stand at 15° to 20° C. without disturbance for three days when it is strained through silk boltingcloth. The proper straining is facilitated by carefully dipping out and straining most of the supernatant liquid and then agitating the remainder and with it rubbing a very small portion of the soil through the straining cloth. The solution is then ready for use, though in addition to being thoroughly stirred before being placed in the culture bottles it is usually diluted by adding pond water in the proportions of from 1 to 4 to 1 to 2, depending upon the degree of density in the appearance of the solution. This culture medium has proved extremely useful to the writer and is now used exclusively for all his Cladocera cultures. No renewal of the solution in a culture bottle is ordinarily required during the life of an individual Cladoceran. Not every make-up of food proves equally satisfactory but persons unaccustomed to handling such culture water quickly learn the proper handling and dilution and very soon obtain excellent results. This soil-manure solution is equally practicable for rearing copepods and some, at least, of the rotifers. Bacteria constitute the principal food element in this culture medium. While a certain amount of uniformity is attainable in such a culture medium, such mass cultures are quite variable and it is obvious that this can scarcely be considered a "standard" food. It is probable that the proper bacteria could be reared on agar plates, definite quantities introduced into the culture bottles at definite intervals and a really standard food thus obtained. ARTHUR M. BANTA STATION FOR EXPERIMENTAL EVOLUTION THE NEBRASKA ACADEMY OF SCIENCE THE thirty-first meeting of the Nebraska Academy of Science, held in Bessey Hall, University of Nebraska, Lincoln, on April 1 and 2, was one of the most interesting in the history of the organization. The attendance was about one hundred, comprising many educational institutions of the state and one or two from adjoining states. The program was so full it was divided into three sections. A very pleasant feature was the annual dinner held in Ellen Smith Hall, followed by President Walker's address, and a general discussion of the needs and interests of the Academy. Dr. Walker made a number of recommendations and suggestions for the advancement of the organization, which has suffered in the past from a lack of the interest and enthusiasm which usually mark the annual meetings. The harvest time of the organization is between the annual meetings, if the officials are sufficiently active and progressive. At the business session on Saturday morning a number of new members and the following officials for the coming year were selected: President, J. C. Jensen, Nebraska Wesleyan University; Vice-president, H. O. Sutton, Teachers' College, Kearney; Secretary, Rose Clark, Teachers' College, Peru; and Treasurer, P. K. Slaymaker, University of Nebraska. A number of amendments to the constitution were approved and the offer of Dr. Sheldon, of temporary headquarters for the academy with the Legislative Bureau, was accepted. University Place was chosen for the 1922 meeting. W. F. HOYT, Secretary Candidates for admission must be graduates of approved colleges or scientific schools with at least two year's instruction, including laboratory work, in Chemistry, and one year each in physics and biology, together with evidence of a reading knowledge of French and German. Each class is limited to 90 students, men and women being admitted on the same terms. Except in unusual circumstances, applications for admission will not be considered after July 1st. If vacancies occur, students from other institutions desiring advanced standing may be admitted to the second or third year provided they fulfill all of our requirements and present exceptional qualifications. The charge for tuition is $250 per annum, payable in three instalments. There are no extra fees except for rental of microscope, certain expensive supplies, and laboratory breakage. The annual announcement and application blanks may be obtained by addressing the Dean of the Johns Hopkins Medical School Washington and Monument Sts. BALTIMORE, MD SUMMER WORK FOR GRADUATES Beginning Tuesday, June 6th, and ending Thursday, July 16th, a course in medical diagnosis, including laboratory exercises in clinical pathology and demonstrations in pathological anatomy, will be offered. The course will be limited to twenty students, fee $100. Applications should be made to the Dean's Office. Louisiana SCHOOL OF MEDICINE (Established in 1834) SUPPLY DEPARTMENT Open the Entire Year Courses of laboratory instruction with lectures are offered in Invertebrate Zoology, Protozoology, Embryology, Physiology and Morphology and Taxonomy of the Algae. Each course requires the full time of the student. Fee, $75. A lecture course on the Philosophical Aspects of Biology and Allied Sciences is also offered. Liv Animals and plants, preserved, liv- GEO. M. GRAY, Curator, Woods Hole, Mass The annual announcement will be sent on application to The Director, Marine Biological Laboratory, Woods Hole, Mass. Yale University SCHOOL OF MEDICINE Affiliated with the New Haven Hospital and New Haven Dispensary 109th Session Reorganized on a full-time basis Entrance Requirements: A minimum of two years (or its equivalent) of college including general biology, physics, general and organic chemistry, physical chemistry or laboratory physics, and either French or German. ALL OF THE GENERAL FACILITIES OF THE UNIVERSITY ARE AVAILABLE TO MEDICAL STUDENTS As the number admitted to each class is limited, applications must be made before July 1. Dean, Yale University School of Medicine NEW HAVEN, CONN. This burette, while sacrificing none of the accuracy possessed by the Hempel, Orsat or McIntosh-Elliott, very greatly decreases the time necessary for an analysis. A complete analysis of coal, water, natural fuel, producer, acetylene, or gasoline gas, comprising determinations of any or all of the following constituents: carbon dioxide, illuminants, oxygen, carbon-monoxide, methane, hydrogen and nitrogen, can be made in from twenty to twenty-five minutes. The saving in time is effected by the elimination of the necessity of shifting the gas from one portion of the apparatus to another. With each outfit we send a 20-page treatise by Mr. Morehead on "Industrial Gases," giving full directions for using the apparatus. Furnished complete with Support, Aspirator Bottles and Rubber Tubing, as illustrated. Also furnished complete as illustrated, but the Burette supplied with Water Jacket for securing constant temperature. Further information and prices on application. E. H. SARGENT & CO. IMPORTERS, MAKERS AND DEALERS IN CHEMICALS 155-165 EAST SUPERIOR STREET CHICAGO, ILL. CADMIUM STANDARD CELLS For use with potentiometers, electrometers, and ballistic galvanemeters, or wherever else a precision standard of electromotive force is needed. Negligible Temperature Coefficient. Contents hermetically sealed in glass so that lowering of electromotive force due to evaporation is impossible. Mounted in moulded box, or unmounted. My comparison certificate accompanies each cell without charge. On November 13, 1916, three normal cadmium cells made by me were certified by the Bureau of Standards as differing from their group of reference cells by less than one part in one hundred thousand, all three having the same value. On March 30 1930, after the lapse of three years and four months, the same three cells were again compared by the Bureau of Standards. The maximum difference among the three was less than one part per hundred thousand, and the maximum difference from their certified value of 1916, was less than one part per hundred thousand. In other words, these cells showed a degree of constancy to ali intents equal to that considered most highly satisfactory, if not remarkable, in the very best type of precision resistance standards. (See Bul. Bur. of Stand. Vol. 5, No. 3, p. 427.) The cells in question were in nowise special. They were made of the materials regularly prepared by me, and were set up with no greater care than that constantly employed in the making of my standards. Marion Eppley, (A.M., Ph.D.) No Laboratory Equipment is complete without some variable resistances. To maintain the high standard of your outfit we suggest the addition of some "Becbro" Sliding Contact Rheostats (Tubular and Stone Types) Thousands of these rheostats have been manufactured and sold by us (the original American Manufacturers) to almost all Universities, Colleges, Technical Schools and Industrial Concerns and have always given entire satisfaction. Write for Bulletin C-5 BECK BROS. 3640-42 North Second Street Philadelphia, Pa. |