The degree of species specificity of the precipitin reaction is still controversial. Since workers have not used similar methods, a part, at least, of these discrepancies may have been due to difference in technic. The specificity or the degree of specificity is of great importance to the one concerned with this test in systematic zoology or in forensic medicine. Uhlenhuth (1, 2) was probably the first to find that there were “group” reactions, i.e., cross reactions when blood sera of related animals were used. Nuttall (3) applied the test extensively to a study of vertebrate and invertebrate relationships. Many others have used the test in a study of serological relationships of all kinds of living matter and it has been employed in medico-legal work, especially in Europe. Friedberger and Collier (4) in 1919 and Friedberger and Jarre (5) in 1920 reported the non-specific reactivities of serum precipitins but in 1922 Manteufel and Berger (6) demonstrated many cases of highly specific precipitins.