The authors of the present communication have worked together for four years, using the spider as an experimental animal (Groh and Lemieux, 1965; Groh and Lemieux, 1965a; Groh and Groh, in press; Groh, Lemieux and St.-Jean, 1966). Previously, one of the authors worked on this project for a period of six years. During the latter four years several drugs, including Thorazine, Haloperidol, Taraxan, Librium, and Surmontil, were tested to determine the changes they cause in the normal geometry of the spider's web. The orb web spinning spider is an animal which cannot survive in nature without its web (the orb web or triangular web is newly built nearly every night), so it is reasonable to suppose that web building is an integral function of the central nervous system, and can be considered as a permanent extension of it. In giving psychopharmacological substances to spiders we were always surprised by the relatively high amount in micrograms usually needed to produce changes in the geometry of the spider's web. In contrast to this, LSD-25 had a registerable action on the geometry when only fractions