usage of the terms substrate and substratum. A substrate (pI.: substrates) is a material utilized by microorganisms, generally as a source of energy. A substratum (pI.: substrata) is asolid surface to which a microorganism mayattach. REFERENCES (1) Marshall, K.C. 1976. Interfaces in Microbial Ecology. Cambridge, MA: Harvard University Press. (2) ZoBell, C.E. 1943. The effect of solid surfaces upon bacterial activity. J. Bacteriol. 46: 39-56. Standing, left to right: Paul Rutter, Rolf Freter, Mike Silverman, lan Robb, Hinrich Mrozek, Frank Dazzo, David Gingell Seated, left to right: Garth Jones, Stanislawa Tylewska, Staffan Kjelleberg, Ellen Rades-Rohkohl, Kevin Marshall Microbial Adhesion and Aggregation, ed. K.C. Marshall, pp. 5-19. Dahlem Konferenzen 1984. Berlin, Heidelberg, New York, Tokyo: Springer-Verlag. Mechanisms of Adhesion Group Report P.R. Rutter, Rapporteur F.B. Dazzo H. Mrozek R. Freter E. Rades-Rohkohl D. GingeIl I.D. Robb G.W. Jones M. Silverman 8. Kjelleberg 8. Tylewska K.C. Marshall INTRODUCTION The subject, Mechanisms of Microbial Attachment, has proved to be a fertile sour ce of argument between both microbiologists and physical chemists. In order to find common ground for discussion, the group endeavored to come to a consensus regarding a number of definitions pertinent to the subject. Some of these are described in the text and others will be found at the end of this report.

One of the most significant occurrences of the twentieth century has been the transition in many countries from tragically high death and birth rates to low rates. In the present book, leading demographers, anthropologists, sociologists, and historians examine the causes of this transition and the reasons why many other countries have not followed suit.

In 1901 the National Bureau of Standards (NBS) was founded to provide standard weights and measures and to be the national physical laboratory for the United States of America. The NBS conducted a lot of research in the fields of science and technology which were reported as "Technological Papers." In 1988 the NBS became what we know now; the National Institute of Standards and Technology (NIST). This is one of those documents written by employees of the NBS.