Estimating Numbers Without Counting

Abstract

IN ecological work it is often necessary to have comparative estimates of the numbers of organisms in a large number of samples. An exact valuation may not be required, but an approximate numerical estimate is always preferable to statements in such terms as few, many, very many, etc. The following method was devised to furnish estimates rapidly and without counting of the numbers of a few of the more important species of the marine plankton where only one or two such species formed the bulk of the samples and where an estimation within ±15 per cent of the actual numbers would be sufficient. Actually the plankton is as a rule so mixed that the method can only be applied to special series of samples and not to normal survey work. It is thought, however, that the method, which is believed to be new, may be of value to workers in other fields: perhaps for estimating the seed production of a large number of plants or samples of small insects all of one species.