Fig. 31.—Ehrenberg, 1795-1876.
In 1845 Stein is engrossed in proposing names for the suborders of infusoria based upon the distribution of cilia upon their bodies. This simple method of classification, as well as the names introduced by Stein, is still in use.
From Stein to Bütschli, one of the present authorities on the group, there were many workers, but with the studies of Bütschli on protozoa we enter the modern epoch.
The importance of these animals in affording a field for experimentation on the simplest expressions of life has already been indicated. Many interesting problems have arisen in connection with recent studies of them. The group embraces the very simplest manifestations of animal life, and the experiments upon the different forms light the way for studies of the vital activities of the higher animals. Some of the protozoa are disease-producing; as the microbe of malaria, of the sleeping sickness, etc., while, as is well known, most diseases that have been traced to specific germs are caused by plants—the bacteria. Many experiments of Maupas, Caulkins and others have a bearing upon the discussions regarding the immortality of the protozoa, an idea which was at one time a feature of Weissmann's theory of heredity. Binet and others have discussed the evidences of psychic life in these micro-organisms, and the daily activity of a protozoan became the field for observation and record in an American laboratory of psychology. The extensive studies of Jennings on the nature of their responses to stimulations form a basis for some of the discussions on animal behavior.
FOOTNOTES:
[2] Kent's Manual of the Infusoria, Vol. I, p. 3. Quotation from the Philosophical Transactions for the year 1677.