1. As found by Sordelli and Mayer, agar adsorbed on bacteria produces agar-reacting antibodies in animals injected with these organisms. 2. False cross-agglutination and precipitin reactions can be produced in sera containing agar-reacting antibodies by organisms grown on agar. Zozaya's publication in this field (3) requires partial revision on this account. 3. There is suggestive immunological...