Summary: THERE have recently appeared in the Press imaginary descriptions of devastations caused among larval fishes and other marine organisms by oil floating on the sea. So far as the present writer knows, these descriptions—some by influential writers—are anticipations of what might occur if oil were a moderately poisonous substance. Oil is certainly noxious, and the writer is fully in agreement with the descriptions which have been given in the Press of the disgusting conditions due to it at high-water mark along our shores and sometimes also at sea, but there is little evidence as yet to show that the kind of oil lost or discharged at sea is even mildly poisonous. For this reason it is necessary to adopt a much more agnostic view than is at present current with regard to the effect of oil on marine organisms. The kind of oil used for fuel on ships at sea is, I am informed, entirely petroleum oil in its crude state or the residue left after the separation of its more valuable and lighter constituents; but it is unlikely that much of these oils will escape or be knowingly discharged from ships, except the heavier residues along with waste lubricating oil. Until it is known what chemical constituents this waste oil contains, it is premature to imagine that it has any serious harmful effect on marine organisms. The more poisonous coal-tar oils are apparently not used as marine fuel oils.