A taxonomic study of the virus of vesicular stomatitis is presented along with evidence additional to that already reported(1) to show the similarity of this virus to that of foot-and-mouth disease. The connection of the two is discussed and the deduction drawn that their generic relationship is close. On the contrary, the differences between these two viruses and the herpetic are sufficiently marked to indicate a lack of generic connection among the three. The results of a comparative study on the effects of particular wave-lengths and energies of monochromatic ultra-violet light on the virus and on Staphylococcus aureus reveal that the adsorption of specific energies by the two is parallel. Since the adsorption of specific energies is an index of chemical character, these experiments suggest that the virus is similar in character and chemical constitution to bacterial protoplasm.