It will be asked, no doubt, by Greek and Latin scholars who have never as yet devoted themselves seriously to a study of Comparative Philology, what is to be gained after all the trouble of learning Sanskrit, and after mastering the works of Bopp, and Benfey, and Curtius? Would a man be a better Greek and Latin scholar for knowing Sanskrit? Would he write better Latin and Greek verse? Would he be better able to read and compare Greek and Latin MSS., and to prepare a critical edition of classical authors? To all these questions I reply both _No_ and _Yes_. If there is one branch of classical philology where the advantages derived from Comparative Philology have been most readily admitted, it is etymology. More than fifty years ago, Otfried Müller told classical scholars that that province at least must be surrendered. And yet it is strange to see how long it takes before old erroneous derivations are exploded and finally expelled from our dictionaries; and how, in spite of all warnings, similarity of sound and similarity of meaning are still considered the chief criteria of Greek and Latin etymologies. I do not address this reproach to classical scholars only; it applies equally to many comparative philologists who, for the sake of some striking similarity of sound and meaning, will now and then break the phonetic laws which they themselves have helped to establish. If we go back to earlier days, we find that Sanskrit scholars who had discovered that one of the names of the god of love in Bengali was _Dipuc_, _i.e._ the inflamer, derived from it by inversion the name of the god of love in Latin, _Cupid_. Sir William Jones identified _Janus_ with the Sanskrit +Gaṇeśa+, _i.e._, lord of hosts,[9] and even later scholars allowed themselves to be tempted to see the Indian prototype of _Ganymedes_ in the +Kaṇva-medhâtithi+ or +Kaṇva-mesha+ of the Veda.[10]