This is a study of the variability of Gomphonema parvulum Kutz.

During the summer of 1948, a biological survey of the Conestoga River Basin in eastern Pennsylvania was conducted by the Academy of Natural Sciences of Philadelphia which aimed at the establishment of biological standards for determining the health of a stream.

In all, over 600 collections of diatoms were made. From the study of these collections, new evidences of affinities between several species were found and the wide variability of certain species especially was noted.