Receiving his Master's degree in June, 1911, Lashley spent the summer at the Carnegie Laboratories at Cold Spring Harbor. There he studied the variability in the number of cirri in the ciliate, Stylonychia. This work attracted the attention of H. S. Jennings, professor of zoology at the Johns Hopkins University, and he offered Lashley a fellowship which was accepted. At Hopkins Karl participated in Jennings' research on paramecia, and also worked with S. O. Mast on the behavior of various invertebrates. His thesis dealt with