Note 16 — Chapter I

Maupas, "Etude des infusoires ciliés" (Arch. de zoologie expérimentale, 1883, pp. 47, 491, 518, 549, in particular). P. Vignon, Recherches de cytologie générale sur les épithéliums, Paris, 1902, p. 655. A profound study of the motions of the Infusoria and a very penetrating criticism of the idea of tropism have been made recently by Jennings (Contributions to the Study of the Behavior of Lower Organisms, Washington, 1904). The "type of behavior" of these lower organisms, as Jennings defines it (pp. 237-252), is unquestionably of the psychological order.