As regards the inflections of verbs, we are bound, if we want a termination for the infinitive, to choose, according to our fundamental principle, the _-r_ of all the Romance languages, because neither the German _-n_, which we have used for other purposes, nor the palatised Slavonic _-t_ (or _-ć_), can be employed, and English possesses no inflection. We require a vowel before the _-r_, the choice of which will be evident from what follows. For the active and passive participles we need only consider _-nt_ and _-t_ respectively, the vowels being also left undecided for the present. The greatest difficulty, however, is caused by the finite tenses, in which we must distinguish present, past, and future. In this respect living languages differ so much amongst themselves that the principle of maximum internationality does not suffice, especially as the inflections of tense are inextricably mixed up with those of person and number, which for our purposes are quite unnecessary. The Delegation Committee have, therefore, for the moment been unable to find anything better than the Esperanto usage of _-as_ for the present, _-is_ for the past, and _-os_ for the future. The same series of vowels may also be employed for the infinitive and participles, so that the normal forms are _-ar_, _-anta_, and _-ata_ (the final vowel _a_ here being the adjectival termination), whilst _-ir_, _-inta_, _-ita_, and _-or_, _-onta_, _-ota_, respectively may be retained for the less frequent cases where one wishes to indicate expressly another tense in the infinitive or participle. A few _à priori_ inflections will not cause much harm in a grammar which is so easy that it may be mastered in half an hour. I have now arrived at the end of my investigation, in which I have endeavoured to show the method whereby the language of the Delegation has been constructed. The result is a language that everyone can easily master, and which possesses the advantage over other languages that it is based on rational scientific principles and, therefore, need not fear that some fine day it will be replaced by another and sensibly different language. Naturally improvements will be effected in details where the fundamental principles have not been sufficiently worked out, but the foundation is sound, and the common auxiliary language of mankind cannot differ very much from our "Internaciona linguo," or, to give it a shorter name, "Interlinguo," or, still shorter, "Ilo" (from the initial letters). OTTO JESPERSEN. APPENDIX CRITICISM OF ESPERANTO In connection with the foregoing some critical remarks on Esperanto may be made, from which one will readily perceive the reasons which made it impossible for the _Délégation pour l'Adoption d'une Langue Internationale_ to adopt Esperanto in its present form as the international auxiliary language.